{ "content": [ { "type": "text", "text": "# grep (info)\n\n## Sections\n\n- **grep**\n- **1 Introduction**\n- **2 Invoking 'grep'** (4 subsections)\n- **3 Regular Expressions** (8 subsections)\n- **4 Usage**\n- **5 Performance**\n- **6 Reporting bugs** (1 subsections)\n- **7 Copying** (2 subsections)\n- **Index**\n\nUse structuredContent.sections for detailed options, examples, and full documentation.\n" } ], "structuredContent": { "command": "grep", "section": "", "mode": "info", "summary": null, "synopsis": null, "tldr_summary": null, "tldr_examples": [], "tldr_source": null, "flags": [], "examples": [], "see_also": [], "section_outline": [ { "name": "grep", "lines": 28, "subsections": [] }, { "name": "1 Introduction", "lines": 14, "subsections": [] }, { "name": "2 Invoking 'grep'", "lines": 19, "subsections": [ { "name": "2.1 Command-line Options", "lines": 471 }, { "name": "2.2 Environment Variables", "lines": 194 }, { "name": "2.3 Exit Status", "lines": 8 }, { "name": "2.4 'grep' Programs", "lines": 38 } ] }, { "name": "3 Regular Expressions", "lines": 27, "subsections": [ { "name": "3.1 Fundamental Structure", "lines": 51 }, { "name": "3.2 Character Classes and Bracket Expressions", "lines": 119 }, { "name": "3.3 The Backslash Character and Special Expressions", "lines": 33 }, { "name": "3.4 Anchoring", "lines": 7 }, { "name": "3.5 Back-references and Subexpressions", "lines": 15 }, { "name": "3.6 Basic vs Extended Regular Expressions", "lines": 35 }, { "name": "3.7 Character Encoding", "lines": 24 }, { "name": "3.8 Matching Non-ASCII and Non-printable Characters", "lines": 32 } ] }, { "name": "4 Usage", "lines": 194, "subsections": [] }, { "name": "5 Performance", "lines": 68, "subsections": [] }, { "name": "6 Reporting bugs", "lines": 11, "subsections": [ { "name": "6.1 Known Bugs", "lines": 19 } ] }, { "name": "7 Copying", "lines": 26, "subsections": [ { "name": "7.1 GNU Free Documentation License", "lines": 445 }, { "name": "ADDENDUM: How to use this License for your documents", "lines": 30 } ] }, { "name": "Index", "lines": 482, "subsections": [] } ], "sections": { "grep": { "content": "'grep' prints lines that contain a match for one or more patterns.\n\nThis manual is for version 3.7 of GNU Grep.\n\nThis manual is for 'grep', a pattern matching engine.\n\nCopyright (C) 1999-2002, 2005, 2008-2021 Free Software Foundation, Inc.\n\nPermission is granted to copy, distribute and/or modify this\ndocument under the terms of the GNU Free Documentation License,\nVersion 1.3 or any later version published by the Free Software\nFoundation; with no Invariant Sections, with no Front-Cover Texts,\nand with no Back-Cover Texts. A copy of the license is included in\nthe section entitled \"GNU Free Documentation License\".\n\n* Menu:\n\n* Introduction:: Introduction.\n* Invoking:: Command-line options, environment, exit status.\n* Regular Expressions:: Regular Expressions.\n* Usage:: Examples.\n* Performance:: Performance tuning.\n* Reporting Bugs:: Reporting Bugs.\n* Copying:: License terms for this manual.\n* Index:: Combined index.\n\nFile: grep.info, Node: Introduction, Next: Invoking, Prev: Top, Up: Top\n", "subsections": [] }, "1 Introduction": { "content": "Given one or more patterns, 'grep' searches input files for matches to\nthe patterns. When it finds a match in a line, it copies the line to\nstandard output (by default), or produces whatever other sort of output\nyou have requested with options.\n\nThough 'grep' expects to do the matching on text, it has no limits on\ninput line length other than available memory, and it can match\narbitrary characters within a line. If the final byte of an input file\nis not a newline, 'grep' silently supplies one. Since newline is also a\nseparator for the list of patterns, there is no way to match newline\ncharacters in a text.\n\nFile: grep.info, Node: Invoking, Next: Regular Expressions, Prev: Introduction, Up: Top\n", "subsections": [] }, "2 Invoking 'grep'": { "content": "The general synopsis of the 'grep' command line is\n\ngrep [OPTION...] [PATTERNS] [FILE...]\n\nThere can be zero or more OPTION arguments, and zero or more FILE\narguments. The PATTERNS argument contains one or more patterns\nseparated by newlines, and is omitted when patterns are given via the\n'-e PATTERNS' or '-f FILE' options. Typically PATTERNS should be quoted\nwhen 'grep' is used in a shell command.\n\n* Menu:\n\n* Command-line Options:: Short and long names, grouped by category.\n* Environment Variables:: POSIX, GNU generic, and GNU grep specific.\n* Exit Status:: Exit status returned by 'grep'.\n* grep Programs:: 'grep' programs.\n\nFile: grep.info, Node: Command-line Options, Next: Environment Variables, Up: Invoking\n", "subsections": [ { "name": "2.1 Command-line Options", "content": "'grep' comes with a rich set of options: some from POSIX and some being\nGNU extensions. Long option names are always a GNU extension, even for\noptions that are from POSIX specifications. Options that are specified\nby POSIX, under their short names, are explicitly marked as such to\nfacilitate POSIX-portable programming. A few option names are provided\nfor compatibility with older or more exotic implementations.\n\n* Menu:\n\n* Generic Program Information::\n* Matching Control::\n* General Output Control::\n* Output Line Prefix Control::\n* Context Line Control::\n* File and Directory Selection::\n* Other Options::\n\nSeveral additional options control which variant of the 'grep'\nmatching engine is used. *Note grep Programs::.\n\nFile: grep.info, Node: Generic Program Information, Next: Matching Control, Up: Command-line Options\n\n\n'--help'\nPrint a usage message briefly summarizing the command-line options\nand the bug-reporting address, then exit.\n\n'-V'\n'--version'\nPrint the version number of 'grep' to the standard output stream.\nThis version number should be included in all bug reports.\n\nFile: grep.info, Node: Matching Control, Next: General Output Control, Prev: Generic Program Information, Up: Command-line Options\n\n\n'-e PATTERNS'\n'--regexp=PATTERNS'\nUse PATTERNS as one or more patterns; newlines within PATTERNS\nseparate each pattern from the next. If this option is used\nmultiple times or is combined with the '-f' ('--file') option,\nsearch for all patterns given. Typically PATTERNS should be quoted\nwhen 'grep' is used in a shell command. ('-e' is specified by\nPOSIX.)\n\n'-f FILE'\n'--file=FILE'\nObtain patterns from FILE, one per line. If this option is used\nmultiple times or is combined with the '-e' ('--regexp') option,\nsearch for all patterns given. The empty file contains zero\npatterns, and therefore matches nothing. ('-f' is specified by\nPOSIX.)\n\n'-i'\n'-y'\n'--ignore-case'\nIgnore case distinctions in patterns and input data, so that\ncharacters that differ only in case match each other. Although\nthis is straightforward when letters differ in case only via\nlowercase-uppercase pairs, the behavior is unspecified in other\nsituations. For example, uppercase \"S\" has an unusual lowercase\ncounterpart \"??\" (Unicode character U+017F, LATIN SMALL LETTER LONG\nS) in many locales, and it is unspecified whether this unusual\ncharacter matches \"S\" or \"s\" even though uppercasing it yields \"S\".\nAnother example: the lowercase German letter \"ss\" (U+00DF, LATIN\nSMALL LETTER SHARP S) is normally capitalized as the two-character\nstring \"SS\" but it does not match \"SS\", and it might not match the\nuppercase letter \"???\" (U+1E9E, LATIN CAPITAL LETTER SHARP S) even\nthough lowercasing the latter yields the former.\n\n'-y' is an obsolete synonym that is provided for compatibility.\n('-i' is specified by POSIX.)\n\n'--no-ignore-case'\nDo not ignore case distinctions in patterns and input data. This\nis the default. This option is useful for passing to shell scripts\nthat already use '-i', in order to cancel its effects because the\ntwo options override each other.\n\n'-v'\n'--invert-match'\nInvert the sense of matching, to select non-matching lines. ('-v'\nis specified by POSIX.)\n\n'-w'\n'--word-regexp'\nSelect only those lines containing matches that form whole words.\nThe test is that the matching substring must either be at the\nbeginning of the line, or preceded by a non-word constituent\ncharacter. Similarly, it must be either at the end of the line or\nfollowed by a non-word constituent character. Word constituent\ncharacters are letters, digits, and the underscore. This option\nhas no effect if '-x' is also specified.\n\nBecause the '-w' option can match a substring that does not begin\nand end with word constituents, it differs from surrounding a\nregular expression with '\\<' and '\\>'. For example, although 'grep\n-w @' matches a line containing only '@', 'grep '\\<@\\>'' cannot\nmatch any line because '@' is not a word constituent. *Note The\nBackslash Character and Special Expressions::.\n\n'-x'\n'--line-regexp'\nSelect only those matches that exactly match the whole line. For\nregular expression patterns, this is like parenthesizing each\npattern and then surrounding it with '^' and '$'. ('-x' is\nspecified by POSIX.)\n\nFile: grep.info, Node: General Output Control, Next: Output Line Prefix Control, Prev: Matching Control, Up: Command-line Options\n\n\n'-c'\n'--count'\nSuppress normal output; instead print a count of matching lines for\neach input file. With the '-v' ('--invert-match') option, count\nnon-matching lines. ('-c' is specified by POSIX.)\n\n'--color[=WHEN]'\n'--colour[=WHEN]'\nSurround the matched (non-empty) strings, matching lines, context\nlines, file names, line numbers, byte offsets, and separators (for\nfields and groups of context lines) with escape sequences to\ndisplay them in color on the terminal. The colors are defined by\nthe environment variable 'GREPCOLORS' and default to\n'ms=01;31:mc=01;31:sl=:cx=:fn=35:ln=32:bn=32:se=36' for bold red\nmatched text, magenta file names, green line numbers, green byte\noffsets, cyan separators, and default terminal colors otherwise.\nThe deprecated environment variable 'GREPCOLOR' is still\nsupported, but its setting does not have priority; it defaults to\n'01;31' (bold red) which only covers the color for matched text.\nWHEN is 'never', 'always', or 'auto'.\n\n'-L'\n'--files-without-match'\nSuppress normal output; instead print the name of each input file\nfrom which no output would normally have been printed.\n\n'-l'\n'--files-with-matches'\nSuppress normal output; instead print the name of each input file\nfrom which output would normally have been printed. Scanning each\ninput file stops upon first match. ('-l' is specified by POSIX.)\n\n'-m NUM'\n'--max-count=NUM'\nStop after the first NUM selected lines. If the input is standard\ninput from a regular file, and NUM selected lines are output,\n'grep' ensures that the standard input is positioned just after the\nlast selected line before exiting, regardless of the presence of\ntrailing context lines. This enables a calling process to resume a\nsearch. For example, the following shell script makes use of it:\n\nwhile grep -m 1 'PATTERN'\ndo\necho xxxx\ndone < FILE\n\nBut the following probably will not work because a pipe is not a\nregular file:\n\n# This probably will not work.\ncat FILE |\nwhile grep -m 1 'PATTERN'\ndo\necho xxxx\ndone\n\nWhen 'grep' stops after NUM selected lines, it outputs any trailing\ncontext lines. When the '-c' or '--count' option is also used,\n'grep' does not output a count greater than NUM. When the '-v' or\n'--invert-match' option is also used, 'grep' stops after outputting\nNUM non-matching lines.\n\n'-o'\n'--only-matching'\nPrint only the matched (non-empty) parts of matching lines, with\neach such part on a separate output line. Output lines use the\nsame delimiters as input, and delimiters are null bytes if '-z'\n('--null-data') is also used (*note Other Options::).\n\n'-q'\n'--quiet'\n'--silent'\nQuiet; do not write anything to standard output. Exit immediately\nwith zero status if any match is found, even if an error was\ndetected. Also see the '-s' or '--no-messages' option. ('-q' is\nspecified by POSIX.)\n\n'-s'\n'--no-messages'\nSuppress error messages about nonexistent or unreadable files.\nPortability note: unlike GNU 'grep', 7th Edition Unix 'grep' did\nnot conform to POSIX, because it lacked '-q' and its '-s' option\nbehaved like GNU 'grep''s '-q' option.(1) USG-style 'grep' also\nlacked '-q' but its '-s' option behaved like GNU 'grep''s.\nPortable shell scripts should avoid both '-q' and '-s' and should\nredirect standard and error output to '/dev/null' instead. ('-s'\nis specified by POSIX.)\n\n---------- Footnotes ----------\n\n(1) Of course, 7th Edition Unix predated POSIX by several years!\n\nFile: grep.info, Node: Output Line Prefix Control, Next: Context Line Control, Prev: General Output Control, Up: Command-line Options\n\n\nWhen several prefix fields are to be output, the order is always file\nname, line number, and byte offset, regardless of the order in which\nthese options were specified.\n\n'-b'\n'--byte-offset'\nPrint the 0-based byte offset within the input file before each\nline of output. If '-o' ('--only-matching') is specified, print\nthe offset of the matching part itself.\n\n'-H'\n'--with-filename'\nPrint the file name for each match. This is the default when there\nis more than one file to search.\n\n'-h'\n'--no-filename'\nSuppress the prefixing of file names on output. This is the\ndefault when there is only one file (or only standard input) to\nsearch.\n\n'--label=LABEL'\nDisplay input actually coming from standard input as input coming\nfrom file LABEL. This can be useful for commands that transform a\nfile's contents before searching; e.g.:\n\ngzip -cd foo.gz | grep --label=foo -H 'some pattern'\n\n'-n'\n'--line-number'\nPrefix each line of output with the 1-based line number within its\ninput file. ('-n' is specified by POSIX.)\n\n'-T'\n'--initial-tab'\nMake sure that the first character of actual line content lies on a\ntab stop, so that the alignment of tabs looks normal. This is\nuseful with options that prefix their output to the actual content:\n'-H', '-n', and '-b'. This may also prepend spaces to output line\nnumbers and byte offsets so that lines from a single file all start\nat the same column.\n\n'-Z'\n'--null'\nOutput a zero byte (the ASCII NUL character) instead of the\ncharacter that normally follows a file name. For example, 'grep\n-lZ' outputs a zero byte after each file name instead of the usual\nnewline. This option makes the output unambiguous, even in the\npresence of file names containing unusual characters like newlines.\nThis option can be used with commands like 'find -print0', 'perl\n-0', 'sort -z', and 'xargs -0' to process arbitrary file names,\neven those that contain newline characters.\n\nFile: grep.info, Node: Context Line Control, Next: File and Directory Selection, Prev: Output Line Prefix Control, Up: Command-line Options\n\n\n\"Context lines\" are non-matching lines that are near a matching line.\nThey are output only if one of the following options are used.\nRegardless of how these options are set, 'grep' never outputs any given\nline more than once. If the '-o' ('--only-matching') option is\nspecified, these options have no effect and a warning is given upon\ntheir use.\n\n'-A NUM'\n'--after-context=NUM'\nPrint NUM lines of trailing context after matching lines.\n\n'-B NUM'\n'--before-context=NUM'\nPrint NUM lines of leading context before matching lines.\n\n'-C NUM'\n'-NUM'\n'--context=NUM'\nPrint NUM lines of leading and trailing output context.\n\n'--group-separator=STRING'\nWhen '-A', '-B' or '-C' are in use, print STRING instead of '--'\nbetween groups of lines.\n\n'--no-group-separator'\nWhen '-A', '-B' or '-C' are in use, do not print a separator\nbetween groups of lines.\n\nHere are some points about how 'grep' chooses the separator to print\nbetween prefix fields and line content:\n\n* Matching lines normally use ':' as a separator between prefix\nfields and actual line content.\n\n* Context (i.e., non-matching) lines use '-' instead.\n\n* When context is not specified, matching lines are simply output one\nright after another.\n\n* When context is specified, lines that are adjacent in the input\nform a group and are output one right after another, while by\ndefault a separator appears between non-adjacent groups.\n\n* The default separator is a '--' line; its presence and appearance\ncan be changed with the options above.\n\n* Each group may contain several matching lines when they are close\nenough to each other that two adjacent groups connect and can merge\ninto a single contiguous one.\n\nFile: grep.info, Node: File and Directory Selection, Next: Other Options, Prev: Context Line Control, Up: Command-line Options\n\n\n'-a'\n'--text'\nProcess a binary file as if it were text; this is equivalent to the\n'--binary-files=text' option.\n\n'--binary-files=TYPE'\nIf a file's data or metadata indicate that the file contains binary\ndata, assume that the file is of type TYPE. Non-text bytes\nindicate binary data; these are either output bytes that are\nimproperly encoded for the current locale (*note Environment\nVariables::), or null input bytes when the '-z' ('--null-data')\noption is not given (*note Other Options::).\n\nBy default, TYPE is 'binary', and 'grep' suppresses output after\nnull input binary data is discovered, and suppresses output lines\nthat contain improperly encoded data. When some output is\nsuppressed, 'grep' follows any output with a one-line message\nsaying that a binary file matches.\n\nIf TYPE is 'without-match', when 'grep' discovers null input binary\ndata it assumes that the rest of the file does not match; this is\nequivalent to the '-I' option.\n\nIf TYPE is 'text', 'grep' processes binary data as if it were text;\nthis is equivalent to the '-a' option.\n\nWhen TYPE is 'binary', 'grep' may treat non-text bytes as line\nterminators even without the '-z' ('--null-data') option. This\nmeans choosing 'binary' versus 'text' can affect whether a pattern\nmatches a file. For example, when TYPE is 'binary' the pattern\n'q$' might match 'q' immediately followed by a null byte, even\nthough this is not matched when TYPE is 'text'. Conversely, when\nTYPE is 'binary' the pattern '.' (period) might not match a null\nbyte.\n\nWarning: The '-a' ('--binary-files=text') option might output\nbinary garbage, which can have nasty side effects if the output is\na terminal and if the terminal driver interprets some of it as\ncommands. On the other hand, when reading files whose text\nencodings are unknown, it can be helpful to use '-a' or to set\n'LCALL='C'' in the environment, in order to find more matches even\nif the matches are unsafe for direct display.\n\n'-D ACTION'\n'--devices=ACTION'\nIf an input file is a device, FIFO, or socket, use ACTION to\nprocess it. If ACTION is 'read', all devices are read just as if\nthey were ordinary files. If ACTION is 'skip', devices, FIFOs, and\nsockets are silently skipped. By default, devices are read if they\nare on the command line or if the '-R' ('--dereference-recursive')\noption is used, and are skipped if they are encountered recursively\nand the '-r' ('--recursive') option is used. This option has no\neffect on a file that is read via standard input.\n\n'-d ACTION'\n'--directories=ACTION'\nIf an input file is a directory, use ACTION to process it. By\ndefault, ACTION is 'read', which means that directories are read\njust as if they were ordinary files (some operating systems and\nfile systems disallow this, and will cause 'grep' to print error\nmessages for every directory or silently skip them). If ACTION is\n'skip', directories are silently skipped. If ACTION is 'recurse',\n'grep' reads all files under each directory, recursively, following\ncommand-line symbolic links and skipping other symlinks; this is\nequivalent to the '-r' option.\n\n'--exclude=GLOB'\nSkip any command-line file with a name suffix that matches the\npattern GLOB, using wildcard matching; a name suffix is either the\nwhole name, or a trailing part that starts with a non-slash\ncharacter immediately after a slash ('/') in the name. When\nsearching recursively, skip any subfile whose base name matches\nGLOB; the base name is the part after the last slash. A pattern\ncan use '*', '?', and '['...']' as wildcards, and '\\' to quote a\nwildcard or backslash character literally.\n\n'--exclude-from=FILE'\nSkip files whose name matches any of the patterns read from FILE\n(using wildcard matching as described under '--exclude').\n\n'--exclude-dir=GLOB'\nSkip any command-line directory with a name suffix that matches the\npattern GLOB. When searching recursively, skip any subdirectory\nwhose base name matches GLOB. Ignore any redundant trailing\nslashes in GLOB.\n\n'-I'\nProcess a binary file as if it did not contain matching data; this\nis equivalent to the '--binary-files=without-match' option.\n\n'--include=GLOB'\nSearch only files whose name matches GLOB, using wildcard matching\nas described under '--exclude'. If contradictory '--include' and\n'--exclude' options are given, the last matching one wins. If no\n'--include' or '--exclude' options match, a file is included unless\nthe first such option is '--include'.\n\n'-r'\n'--recursive'\nFor each directory operand, read and process all files in that\ndirectory, recursively. Follow symbolic links on the command line,\nbut skip symlinks that are encountered recursively. Note that if\nno file operand is given, grep searches the working directory.\nThis is the same as the '--directories=recurse' option.\n\n'-R'\n'--dereference-recursive'\nFor each directory operand, read and process all files in that\ndirectory, recursively, following all symbolic links.\n\nFile: grep.info, Node: Other Options, Prev: File and Directory Selection, Up: Command-line Options\n\n\n'--'\nDelimit the option list. Later arguments, if any, are treated as\noperands even if they begin with '-'. For example, 'grep PAT --\n-file1 file2' searches for the pattern PAT in the files named\n'-file1' and 'file2'.\n\n'--line-buffered'\nUse line buffering for standard output, regardless of output\ndevice. By default, standard output is line buffered for\ninteractive devices, and is fully buffered otherwise. With full\nbuffering, the output buffer is flushed when full; with line\nbuffering, the buffer is also flushed after every output line. The\nbuffer size is system dependent.\n\n'-U'\n'--binary'\nOn platforms that distinguish between text and binary I/O, use the\nlatter when reading and writing files other than the user's\nterminal, so that all input bytes are read and written as-is. This\noverrides the default behavior where 'grep' follows the operating\nsystem's advice whether to use text or binary I/O. On MS-Windows\nwhen 'grep' uses text I/O it reads a carriage return-newline pair\nas a newline and a Control-Z as end-of-file, and it writes a\nnewline as a carriage return-newline pair.\n\nWhen using text I/O '--byte-offset' ('-b') counts and\n'--binary-files' heuristics apply to input data after text-I/O\nprocessing. Also, the '--binary-files' heuristics need not agree\nwith the '--binary' option; that is, they may treat the data as\ntext even if '--binary' is given, or vice versa. *Note File and\nDirectory Selection::.\n\nThis option has no effect on GNU and other POSIX-compatible\nplatforms, which do not distinguish text from binary I/O.\n\n'-z'\n'--null-data'\nTreat input and output data as sequences of lines, each terminated\nby a zero byte (the ASCII NUL character) instead of a newline.\nLike the '-Z' or '--null' option, this option can be used with\ncommands like 'sort -z' to process arbitrary file names.\n\nFile: grep.info, Node: Environment Variables, Next: Exit Status, Prev: Command-line Options, Up: Invoking\n" }, { "name": "2.2 Environment Variables", "content": "The behavior of 'grep' is affected by the following environment\nvariables.\n\nThe locale for category 'LCFOO' is specified by examining the three\nenvironment variables 'LCALL', 'LCFOO', and 'LANG', in that order.\nThe first of these variables that is set specifies the locale. For\nexample, if 'LCALL' is not set, but 'LCCOLLATE' is set to 'ptBR',\nthen the Brazilian Portuguese locale is used for the 'LCCOLLATE'\ncategory. As a special case for 'LCMESSAGES' only, the environment\nvariable 'LANGUAGE' can contain a colon-separated list of languages that\noverrides the three environment variables that ordinarily specify the\n'LCMESSAGES' category. The 'C' locale is used if none of these\nenvironment variables are set, if the locale catalog is not installed,\nor if 'grep' was not compiled with national language support (NLS). The\nshell command 'locale -a' lists locales that are currently available.\n\nMany of the environment variables in the following list let you\ncontrol highlighting using Select Graphic Rendition (SGR) commands\ninterpreted by the terminal or terminal emulator. (See the section in\nthe documentation of your text terminal for permitted values and their\nmeanings as character attributes.) These substring values are integers\nin decimal representation and can be concatenated with semicolons.\n'grep' takes care of assembling the result into a complete SGR sequence\n('\\33['...'m'). Common values to concatenate include '1' for bold, '4'\nfor underline, '5' for blink, '7' for inverse, '39' for default\nforeground color, '30' to '37' for foreground colors, '90' to '97' for\n16-color mode foreground colors, '38;5;0' to '38;5;255' for 88-color and\n256-color modes foreground colors, '49' for default background color,\n'40' to '47' for background colors, '100' to '107' for 16-color mode\nbackground colors, and '48;5;0' to '48;5;255' for 88-color and 256-color\nmodes background colors.\n\nThe two-letter names used in the 'GREPCOLORS' environment variable\n(and some of the others) refer to terminal \"capabilities,\" the ability\nof a terminal to highlight text, or change its color, and so on. These\ncapabilities are stored in an online database and accessed by the\n'terminfo' library.\n\n'GREPCOLOR'\nThis variable specifies the color used to highlight matched\n(non-empty) text. It is deprecated in favor of 'GREPCOLORS', but\nstill supported. The 'mt', 'ms', and 'mc' capabilities of\n'GREPCOLORS' have priority over it. It can only specify the color\nused to highlight the matching non-empty text in any matching line\n(a selected line when the '-v' command-line option is omitted, or a\ncontext line when '-v' is specified). The default is '01;31',\nwhich means a bold red foreground text on the terminal's default\nbackground.\n\n'GREPCOLORS'\nThis variable specifies the colors and other attributes used to\nhighlight various parts of the output. Its value is a\ncolon-separated list of 'terminfo' capabilities that defaults to\n'ms=01;31:mc=01;31:sl=:cx=:fn=35:ln=32:bn=32:se=36' with the 'rv'\nand 'ne' boolean capabilities omitted (i.e., false). Supported\ncapabilities are as follows.\n\n'sl='\nSGR substring for whole selected lines (i.e., matching lines\nwhen the '-v' command-line option is omitted, or non-matching\nlines when '-v' is specified). If however the boolean 'rv'\ncapability and the '-v' command-line option are both\nspecified, it applies to context matching lines instead. The\ndefault is empty (i.e., the terminal's default color pair).\n\n'cx='\nSGR substring for whole context lines (i.e., non-matching\nlines when the '-v' command-line option is omitted, or\nmatching lines when '-v' is specified). If however the\nboolean 'rv' capability and the '-v' command-line option are\nboth specified, it applies to selected non-matching lines\ninstead. The default is empty (i.e., the terminal's default\ncolor pair).\n\n'rv'\nBoolean value that reverses (swaps) the meanings of the 'sl='\nand 'cx=' capabilities when the '-v' command-line option is\nspecified. The default is false (i.e., the capability is\nomitted).\n\n'mt=01;31'\nSGR substring for matching non-empty text in any matching line\n(i.e., a selected line when the '-v' command-line option is\nomitted, or a context line when '-v' is specified). Setting\nthis is equivalent to setting both 'ms=' and 'mc=' at once to\nthe same value. The default is a bold red text foreground\nover the current line background.\n\n'ms=01;31'\nSGR substring for matching non-empty text in a selected line.\n(This is used only when the '-v' command-line option is\nomitted.) The effect of the 'sl=' (or 'cx=' if 'rv')\ncapability remains active when this takes effect. The default\nis a bold red text foreground over the current line\nbackground.\n\n'mc=01;31'\nSGR substring for matching non-empty text in a context line.\n(This is used only when the '-v' command-line option is\nspecified.) The effect of the 'cx=' (or 'sl=' if 'rv')\ncapability remains active when this takes effect. The default\nis a bold red text foreground over the current line\nbackground.\n\n'fn=35'\nSGR substring for file names prefixing any content line. The\ndefault is a magenta text foreground over the terminal's\ndefault background.\n\n'ln=32'\nSGR substring for line numbers prefixing any content line.\nThe default is a green text foreground over the terminal's\ndefault background.\n\n'bn=32'\nSGR substring for byte offsets prefixing any content line.\nThe default is a green text foreground over the terminal's\ndefault background.\n\n'se=36'\nSGR substring for separators that are inserted between\nselected line fields (':'), between context line fields ('-'),\nand between groups of adjacent lines when nonzero context is\nspecified ('--'). The default is a cyan text foreground over\nthe terminal's default background.\n\n'ne'\nBoolean value that prevents clearing to the end of line using\nErase in Line (EL) to Right ('\\33[K') each time a colorized\nitem ends. This is needed on terminals on which EL is not\nsupported. It is otherwise useful on terminals for which the\n'backcolorerase' ('bce') boolean 'terminfo' capability does\nnot apply, when the chosen highlight colors do not affect the\nbackground, or when EL is too slow or causes too much flicker.\nThe default is false (i.e., the capability is omitted).\n\nNote that boolean capabilities have no '='... part. They are\nomitted (i.e., false) by default and become true when specified.\n\n'LCALL'\n'LCCOLLATE'\n'LANG'\nThese variables specify the locale for the 'LCCOLLATE' category,\nwhich might affect how range expressions like '[a-z]' are\ninterpreted.\n\n'LCALL'\n'LCCTYPE'\n'LANG'\nThese variables specify the locale for the 'LCCTYPE' category,\nwhich determines the type of characters, e.g., which characters are\nwhitespace. This category also determines the character encoding.\n*Note Character Encoding::.\n\n'LANGUAGE'\n'LCALL'\n'LCMESSAGES'\n'LANG'\nThese variables specify the locale for the 'LCMESSAGES' category,\nwhich determines the language that 'grep' uses for messages. The\ndefault 'C' locale uses American English messages.\n\n'POSIXLYCORRECT'\nIf set, 'grep' behaves as POSIX requires; otherwise, 'grep' behaves\nmore like other GNU programs. POSIX requires that options that\nfollow file names must be treated as file names; by default, such\noptions are permuted to the front of the operand list and are\ntreated as options. Also, 'POSIXLYCORRECT' disables special\nhandling of an invalid bracket expression. *Note\ninvalid-bracket-expr::.\n\n'NGNUnonoptionargvflags'\n(Here 'N' is 'grep''s numeric process ID.) If the Ith character of\nthis environment variable's value is '1', do not consider the Ith\noperand of 'grep' to be an option, even if it appears to be one. A\nshell can put this variable in the environment for each command it\nruns, specifying which operands are the results of file name\nwildcard expansion and therefore should not be treated as options.\nThis behavior is available only with the GNU C library, and only\nwhen 'POSIXLYCORRECT' is not set.\n\nThe 'GREPOPTIONS' environment variable of 'grep' 2.20 and earlier is\nno longer supported, as it caused problems when writing portable\nscripts. To make arbitrary changes to how 'grep' works, you can use an\nalias or script instead. For example, if 'grep' is in the directory\n'/usr/bin' you can prepend '$HOME/bin' to your 'PATH' and create an\nexecutable script '$HOME/bin/grep' containing the following:\n\n#! /bin/sh\nexport PATH=/usr/bin\nexec grep --color=auto --devices=skip \"$@\"\n\nFile: grep.info, Node: Exit Status, Next: grep Programs, Prev: Environment Variables, Up: Invoking\n" }, { "name": "2.3 Exit Status", "content": "Normally the exit status is 0 if a line is selected, 1 if no lines were\nselected, and 2 if an error occurred. However, if the '-q' or '--quiet'\nor '--silent' option is used and a line is selected, the exit status is\n0 even if an error occurred. Other 'grep' implementations may exit with\nstatus greater than 2 on error.\n\nFile: grep.info, Node: grep Programs, Prev: Exit Status, Up: Invoking\n" }, { "name": "2.4 'grep' Programs", "content": "'grep' searches the named input files for lines containing a match to\nthe given patterns. By default, 'grep' prints the matching lines. A\nfile named '-' stands for standard input. If no input is specified,\n'grep' searches the working directory '.' if given a command-line option\nspecifying recursion; otherwise, 'grep' searches standard input. There\nare four major variants of 'grep', controlled by the following options.\n\n'-G'\n'--basic-regexp'\nInterpret patterns as basic regular expressions (BREs). This is\nthe default.\n\n'-E'\n'--extended-regexp'\nInterpret patterns as extended regular expressions (EREs). ('-E'\nis specified by POSIX.)\n\n'-F'\n'--fixed-strings'\nInterpret patterns as fixed strings, not regular expressions.\n('-F' is specified by POSIX.)\n\n'-P'\n'--perl-regexp'\nInterpret patterns as Perl-compatible regular expressions (PCREs).\nPCRE support is here to stay, but consider this option experimental\nwhen combined with the '-z' ('--null-data') option, and note that\n'grep -P' may warn of unimplemented features. *Note Other\nOptions::.\n\nIn addition, two variant programs 'egrep' and 'fgrep' are available.\n'egrep' is the same as 'grep -E'. 'fgrep' is the same as 'grep -F'.\nDirect invocation as either 'egrep' or 'fgrep' is deprecated, but is\nprovided to allow historical applications that rely on them to run\nunmodified.\n\nFile: grep.info, Node: Regular Expressions, Next: Usage, Prev: Invoking, Up: Top\n" } ] }, "3 Regular Expressions": { "content": "A \"regular expression\" is a pattern that describes a set of strings.\nRegular expressions are constructed analogously to arithmetic\nexpressions, by using various operators to combine smaller expressions.\n'grep' understands three different versions of regular expression\nsyntax: basic (BRE), extended (ERE), and Perl-compatible (PCRE). In GNU\n'grep', there is no difference in available functionality between the\nbasic and extended syntaxes. In other implementations, basic regular\nexpressions are less powerful. The following description applies to\nextended regular expressions; differences for basic regular expressions\nare summarized afterwards. Perl-compatible regular expressions give\nadditional functionality, and are documented in the pcresyntax(3) and\npcrepattern(3) manual pages, but work only if PCRE is available in the\nsystem.\n\n* Menu:\n\n* Fundamental Structure::\n* Character Classes and Bracket Expressions::\n* The Backslash Character and Special Expressions::\n* Anchoring::\n* Back-references and Subexpressions::\n* Basic vs Extended::\n* Character Encoding::\n* Matching Non-ASCII::\n\nFile: grep.info, Node: Fundamental Structure, Next: Character Classes and Bracket Expressions, Up: Regular Expressions\n", "subsections": [ { "name": "3.1 Fundamental Structure", "content": "In regular expressions, the characters '.?*+{|()[\\^$' are \"special\ncharacters\" and have uses described below. All other characters are\n\"ordinary characters\", and each ordinary character is a regular\nexpression that matches itself.\n\nThe period '.' matches any single character. It is unspecified\nwhether '.' matches an encoding error.\n\nA regular expression may be followed by one of several repetition\noperators; the operators beginning with '{' are called \"interval\nexpressions\".\n\n'?'\nThe preceding item is optional and is matched at most once.\n\n'*'\nThe preceding item is matched zero or more times.\n\n'+'\nThe preceding item is matched one or more times.\n\n'{N}'\nThe preceding item is matched exactly N times.\n\n'{N,}'\nThe preceding item is matched N or more times.\n\n'{,M}'\nThe preceding item is matched at most M times. This is a GNU\nextension.\n\n'{N,M}'\nThe preceding item is matched at least N times, but not more than M\ntimes.\n\nThe empty regular expression matches the empty string. Two regular\nexpressions may be concatenated; the resulting regular expression\nmatches any string formed by concatenating two substrings that\nrespectively match the concatenated expressions.\n\nTwo regular expressions may be joined by the infix operator '|'; the\nresulting regular expression matches any string matching either\nalternate expression.\n\nRepetition takes precedence over concatenation, which in turn takes\nprecedence over alternation. A whole expression may be enclosed in\nparentheses to override these precedence rules and form a subexpression.\nAn unmatched ')' matches just itself.\n\nFile: grep.info, Node: Character Classes and Bracket Expressions, Next: The Backslash Character and Special Expressions, Prev: Fundamental Structure, Up: Regular Expressions\n" }, { "name": "3.2 Character Classes and Bracket Expressions", "content": "A \"bracket expression\" is a list of characters enclosed by '[' and ']'.\nIt matches any single character in that list. If the first character of\nthe list is the caret '^', then it matches any character *not* in the\nlist, and it is unspecified whether it matches an encoding error. For\nexample, the regular expression '[0123456789]' matches any single digit,\nwhereas '[^()]' matches any single character that is not an opening or\nclosing parenthesis, and might or might not match an encoding error.\n\nWithin a bracket expression, a \"range expression\" consists of two\ncharacters separated by a hyphen. It matches any single character that\nsorts between the two characters, inclusive. In the default C locale,\nthe sorting sequence is the native character order; for example, '[a-d]'\nis equivalent to '[abcd]'. In other locales, the sorting sequence is\nnot specified, and '[a-d]' might be equivalent to '[abcd]' or to\n'[aBbCcDd]', or it might fail to match any character, or the set of\ncharacters that it matches might even be erratic. To obtain the\ntraditional interpretation of bracket expressions, you can use the 'C'\nlocale by setting the 'LCALL' environment variable to the value 'C'.\n\nFinally, certain named classes of characters are predefined within\nbracket expressions, as follows. Their interpretation depends on the\n'LCCTYPE' locale; for example, '[[:alnum:]]' means the character class\nof numbers and letters in the current locale.\n\n'[:alnum:]'\nAlphanumeric characters: '[:alpha:]' and '[:digit:]'; in the 'C'\nlocale and ASCII character encoding, this is the same as\n'[0-9A-Za-z]'.\n\n'[:alpha:]'\nAlphabetic characters: '[:lower:]' and '[:upper:]'; in the 'C'\nlocale and ASCII character encoding, this is the same as\n'[A-Za-z]'.\n\n'[:blank:]'\nBlank characters: space and tab.\n\n'[:cntrl:]'\nControl characters. In ASCII, these characters have octal codes\n000 through 037, and 177 (DEL). In other character sets, these are\nthe equivalent characters, if any.\n\n'[:digit:]'\nDigits: '0 1 2 3 4 5 6 7 8 9'.\n\n'[:graph:]'\nGraphical characters: '[:alnum:]' and '[:punct:]'.\n\n'[:lower:]'\nLower-case letters; in the 'C' locale and ASCII character encoding,\nthis is 'a b c d e f g h i j k l m n o p q r s t u v w x y z'.\n\n'[:print:]'\nPrintable characters: '[:alnum:]', '[:punct:]', and space.\n\n'[:punct:]'\nPunctuation characters; in the 'C' locale and ASCII character\nencoding, this is '! \" # $ % & ' ( ) * + , - . / : ; < = > ? @ [ \\\n] ^ ` { | } ~'.\n\n'[:space:]'\nSpace characters: in the 'C' locale, this is tab, newline, vertical\ntab, form feed, carriage return, and space. *Note Usage::, for\nmore discussion of matching newlines.\n\n'[:upper:]'\nUpper-case letters: in the 'C' locale and ASCII character encoding,\nthis is 'A B C D E F G H I J K L M N O P Q R S T U V W X Y Z'.\n\n'[:xdigit:]'\nHexadecimal digits: '0 1 2 3 4 5 6 7 8 9 A B C D E F a b c d e f'.\n\nNote that the brackets in these class names are part of the symbolic\nnames, and must be included in addition to the brackets delimiting the\nbracket expression.\n\nIf you mistakenly omit the outer brackets, and search for say,\n'[:upper:]', GNU 'grep' prints a diagnostic and exits with status 2, on\nthe assumption that you did not intend to search for the nominally\nequivalent regular expression: '[:epru]'. Set the 'POSIXLYCORRECT'\nenvironment variable to disable this feature.\n\nSpecial characters lose their special meaning inside bracket\nexpressions.\n\n']'\nends the bracket expression if it's not the first list item. So,\nif you want to make the ']' character a list item, you must put it\nfirst.\n\n'[.'\nrepresents the open collating symbol.\n\n'.]'\nrepresents the close collating symbol.\n\n'[='\nrepresents the open equivalence class.\n\n'=]'\nrepresents the close equivalence class.\n\n'[:'\nrepresents the open character class symbol, and should be followed\nby a valid character class name.\n\n':]'\nrepresents the close character class symbol.\n\n'-'\nrepresents the range if it's not first or last in a list or the\nending point of a range.\n\n'^'\nrepresents the characters not in the list. If you want to make the\n'^' character a list item, place it anywhere but first.\n\nFile: grep.info, Node: The Backslash Character and Special Expressions, Next: Anchoring, Prev: Character Classes and Bracket Expressions, Up: Regular Expressions\n" }, { "name": "3.3 The Backslash Character and Special Expressions", "content": "The '\\' character followed by a special character is a regular\nexpression that matches the special character. The '\\' character, when\nfollowed by certain ordinary characters, takes a special meaning:\n\n'\\b'\nMatch the empty string at the edge of a word.\n\n'\\B'\nMatch the empty string provided it's not at the edge of a word.\n\n'\\<'\nMatch the empty string at the beginning of a word.\n\n'\\>'\nMatch the empty string at the end of a word.\n\n'\\w'\nMatch word constituent, it is a synonym for '[[:alnum:]]'.\n\n'\\W'\nMatch non-word constituent, it is a synonym for '[^[:alnum:]]'.\n\n'\\s'\nMatch whitespace, it is a synonym for '[[:space:]]'.\n\n'\\S'\nMatch non-whitespace, it is a synonym for '[^[:space:]]'.\n\nFor example, '\\brat\\b' matches the separate word 'rat', '\\Brat\\B'\nmatches 'crate' but not 'furry rat'.\n\nFile: grep.info, Node: Anchoring, Next: Back-references and Subexpressions, Prev: The Backslash Character and Special Expressions, Up: Regular Expressions\n" }, { "name": "3.4 Anchoring", "content": "The caret '^' and the dollar sign '$' are special characters that\nrespectively match the empty string at the beginning and end of a line.\nThey are termed \"anchors\", since they force the match to be \"anchored\"\nto beginning or end of a line, respectively.\n\nFile: grep.info, Node: Back-references and Subexpressions, Next: Basic vs Extended, Prev: Anchoring, Up: Regular Expressions\n" }, { "name": "3.5 Back-references and Subexpressions", "content": "The back-reference '\\N', where N is a single nonzero digit, matches the\nsubstring previously matched by the Nth parenthesized subexpression of\nthe regular expression. For example, '(a)\\1' matches 'aa'. If the\nparenthesized subexpression does not participate in the match, the\nback-reference makes the whole match fail; for example, '(a)*\\1' fails\nto match 'a'. If the parenthesized subexpression matches more than one\nsubstring, the back-reference refers to the last matched substring; for\nexample, '^(ab*)*\\1$' matches 'ababbabb' but not 'ababbab'. When\nmultiple regular expressions are given with '-e' or from a file ('-f\nFILE'), back-references are local to each expression.\n\n*Note Known Bugs::, for some known problems with back-references.\n\nFile: grep.info, Node: Basic vs Extended, Next: Character Encoding, Prev: Back-references and Subexpressions, Up: Regular Expressions\n" }, { "name": "3.6 Basic vs Extended Regular Expressions", "content": "In basic regular expressions the characters '?', '+', '{', '|', '(', and\n')' lose their special meaning; instead use the backslashed versions\n'\\?', '\\+', '\\{', '\\|', '\\(', and '\\)'. Also, a backslash is needed\nbefore an interval expression's closing '}', and an unmatched '\\)' is\ninvalid.\n\nPortable scripts should avoid the following constructs, as POSIX says\nthey produce undefined results:\n\n* Extended regular expressions that use back-references.\n* Basic regular expressions that use '\\?', '\\+', or '\\|'.\n* Empty parenthesized regular expressions like '()'.\n* Empty alternatives (as in, e.g, 'a|').\n* Repetition operators that immediately follow empty expressions,\nunescaped '$', or other repetition operators.\n* A backslash escaping an ordinary character (e.g., '\\S'), unless it\nis a back-reference.\n* An unescaped '[' that is not part of a bracket expression.\n* In extended regular expressions, an unescaped '{' that is not part\nof an interval expression.\n\nTraditional 'egrep' did not support interval expressions and some\n'egrep' implementations use '\\{' and '\\}' instead, so portable scripts\nshould avoid interval expressions in 'grep -E' patterns and should use\n'[{]' to match a literal '{'.\n\nGNU 'grep -E' attempts to support traditional usage by assuming that\n'{' is not special if it would be the start of an invalid interval\nexpression. For example, the command 'grep -E '{1'' searches for the\ntwo-character string '{1' instead of reporting a syntax error in the\nregular expression. POSIX allows this behavior as an extension, but\nportable scripts should avoid it.\n\nFile: grep.info, Node: Character Encoding, Next: Matching Non-ASCII, Prev: Basic vs Extended, Up: Regular Expressions\n" }, { "name": "3.7 Character Encoding", "content": "The 'LCCTYPE' locale specifies the encoding of characters in patterns\nand data, that is, whether text is encoded in UTF-8, ASCII, or some\nother encoding. *Note Environment Variables::.\n\nIn the 'C' or 'POSIX' locale, every character is encoded as a single\nbyte and every byte is a valid character. In more-complex encodings\nsuch as UTF-8, a sequence of multiple bytes may be needed to represent a\ncharacter, and some bytes may be encoding errors that do not contribute\nto the representation of any character. POSIX does not specify the\nbehavior of 'grep' when patterns or input data contain encoding errors\nor null characters, so portable scripts should avoid such usage. As an\nextension to POSIX, GNU 'grep' treats null characters like any other\ncharacter. However, unless the '-a' ('--binary-files=text') option is\nused, the presence of null characters in input or of encoding errors in\noutput causes GNU 'grep' to treat the file as binary and suppress\ndetails about matches. *Note File and Directory Selection::.\n\nRegardless of locale, the 103 characters in the POSIX Portable\nCharacter Set (a subset of ASCII) are always encoded as a single byte,\nand the 128 ASCII characters have their usual single-byte encodings on\nall but oddball platforms.\n\nFile: grep.info, Node: Matching Non-ASCII, Prev: Character Encoding, Up: Regular Expressions\n" }, { "name": "3.8 Matching Non-ASCII and Non-printable Characters", "content": "In a regular expression, non-ASCII and non-printable characters other\nthan newline are not special, and represent themselves. For example, in\na locale using UTF-8 the command 'grep '?? ??'' (where the white space\nbetween '??' and the '??' is a tab character) searches for '??' (Unicode\ncharacter U+039B GREEK CAPITAL LETTER LAMBDA), followed by a tab (U+0009\nTAB), followed by '??' (U+03C9 GREEK SMALL LETTER OMEGA).\n\nSuppose you want to limit your pattern to only printable characters\n(or even only printable ASCII characters) to keep your script readable\nor portable, but you also want to match specific non-ASCII or non-null\nnon-printable characters. If you are using the '-P' ('--perl-regexp')\noption, PCREs give you several ways to do this. Otherwise, if you are\nusing Bash, the GNU project's shell, you can represent these characters\nvia ANSI-C quoting. For example, the Bash commands 'grep $'??\\t??'' and\n'grep $'\\u039B\\t\\u03C9'' both search for the same three-character string\n'?? ??' mentioned earlier. However, because Bash translates ANSI-C\nquoting before 'grep' sees the pattern, this technique should not be\nused to match printable ASCII characters; for example, 'grep $'\\u005E''\nis equivalent to 'grep '^'' and matches any line, not just lines\ncontaining the character '^' (U+005E CIRCUMFLEX ACCENT).\n\nSince PCREs and ANSI-C quoting are GNU extensions to POSIX, portable\nshell scripts written in ASCII should use other methods to match\nspecific non-ASCII characters. For example, in a UTF-8 locale the\ncommand 'grep \"$(printf '\\316\\233\\t\\317\\211\\n')\"' is a portable albeit\nhard-to-read alternative to Bash's 'grep $'??\\t??''. However, none of\nthese techniques will let you put a null character directly into a\ncommand-line pattern; null characters can appear only in a pattern\nspecified via the '-f' ('--file') option.\n\nFile: grep.info, Node: Usage, Next: Performance, Prev: Regular Expressions, Up: Top\n" } ] }, "4 Usage": { "content": "Here is an example command that invokes GNU 'grep':\n\ngrep -i 'hello.*world' menu.h main.c\n\nThis lists all lines in the files 'menu.h' and 'main.c' that contain the\nstring 'hello' followed by the string 'world'; this is because '.*'\nmatches zero or more characters within a line. *Note Regular\nExpressions::. The '-i' option causes 'grep' to ignore case, causing it\nto match the line 'Hello, world!', which it would not otherwise match.\n\nHere is a more complex example, showing the location and contents of\nany line containing 'f' and ending in '.c', within all files in the\ncurrent directory whose names start with non-'.', contain 'g', and end\nin '.h'. The '-n' option outputs line numbers, the '--' argument treats\nany later arguments as file names not options even if '*g*.h' expands to\na file name that starts with '-', and the empty file '/dev/null' causes\nfile names to be output even if only one file name happens to be of the\nform '*g*.h'.\n\ngrep -n -- 'f.*\\.c$' *g*.h /dev/null\n\nNote that the regular expression syntax used in the pattern differs from\nthe globbing syntax that the shell uses to match file names.\n\n*Note Invoking::, for more details about how to invoke 'grep'.\n\nHere are some common questions and answers about 'grep' usage.\n\n1. How can I list just the names of matching files?\n\ngrep -l 'main' test-*.c\n\nlists names of 'test-*.c' files in the current directory whose\ncontents mention 'main'.\n\n2. How do I search directories recursively?\n\ngrep -r 'hello' /home/gigi\n\nsearches for 'hello' in all files under the '/home/gigi' directory.\nFor more control over which files are searched, use 'find' and\n'grep'. For example, the following command searches only C files:\n\nfind /home/gigi -name '*.c' ! -type d \\\n-exec grep -H 'hello' '{}' +\n\nThis differs from the command:\n\ngrep -H 'hello' /home/gigi/*.c\n\nwhich merely looks for 'hello' in non-hidden C files in\n'/home/gigi' whose names end in '.c'. The 'find' command line\nabove is more similar to the command:\n\ngrep -r --include='*.c' 'hello' /home/gigi\n\n3. What if a pattern or file has a leading '-'?\n\ngrep -- '--cut here--' *\n\nsearches for all lines matching '--cut here--'. Without '--',\n'grep' would attempt to parse '--cut here--' as a list of options,\nand there would be similar problems with any file names beginning\nwith '-'.\n\nAlternatively, you can prevent misinterpretation of leading '-' by\nusing '-e' for patterns and leading './' for files:\n\ngrep -e '--cut here--' ./*\n\n4. Suppose I want to search for a whole word, not a part of a word?\n\ngrep -w 'hello' test*.log\n\nsearches only for instances of 'hello' that are entire words; it\ndoes not match 'Othello'. For more control, use '\\<' and '\\>' to\nmatch the start and end of words. For example:\n\ngrep 'hello\\>' test*.log\n\nsearches only for words ending in 'hello', so it matches the word\n'Othello'.\n\n5. How do I output context around the matching lines?\n\ngrep -C 2 'hello' test*.log\n\nprints two lines of context around each matching line.\n\n6. How do I force 'grep' to print the name of the file?\n\nAppend '/dev/null':\n\ngrep 'eli' /etc/passwd /dev/null\n\ngets you:\n\n/etc/passwd:eli:x:2098:1000:Eli Smith:/home/eli:/bin/bash\n\nAlternatively, use '-H', which is a GNU extension:\n\ngrep -H 'eli' /etc/passwd\n\n7. Why do people use strange regular expressions on 'ps' output?\n\nps -ef | grep '[c]ron'\n\nIf the pattern had been written without the square brackets, it\nwould have matched not only the 'ps' output line for 'cron', but\nalso the 'ps' output line for 'grep'. Note that on some platforms,\n'ps' limits the output to the width of the screen; 'grep' does not\nhave any limit on the length of a line except the available memory.\n\n8. Why does 'grep' report \"Binary file matches\"?\n\nIf 'grep' listed all matching \"lines\" from a binary file, it would\nprobably generate output that is not useful, and it might even muck\nup your display. So GNU 'grep' suppresses output from files that\nappear to be binary files. To force GNU 'grep' to output lines\neven from files that appear to be binary, use the '-a' or\n'--binary-files=text' option. To eliminate the \"Binary file\nmatches\" messages, use the '-I' or '--binary-files=without-match'\noption, or the '-s' or '--no-messages' option.\n\n9. Why doesn't 'grep -lv' print non-matching file names?\n\n'grep -lv' lists the names of all files containing one or more\nlines that do not match. To list the names of all files that\ncontain no matching lines, use the '-L' or '--files-without-match'\noption.\n\n10. I can do \"OR\" with '|', but what about \"AND\"?\n\ngrep 'paul' /etc/motd | grep 'franc,ois'\n\nfinds all lines that contain both 'paul' and 'franc,ois'.\n\n11. Why does the empty pattern match every input line?\n\nThe 'grep' command searches for lines that contain strings that\nmatch a pattern. Every line contains the empty string, so an empty\npattern causes 'grep' to find a match on each line. It is not the\nonly such pattern: '^', '$', and many other patterns cause 'grep'\nto match every line.\n\nTo match empty lines, use the pattern '^$'. To match blank lines,\nuse the pattern '^[[:blank:]]*$'. To match no lines at all, use\nthe command 'grep -f /dev/null'.\n\n12. How can I search in both standard input and in files?\n\nUse the special file name '-':\n\ncat /etc/passwd | grep 'alain' - /etc/motd\n\n13. Why is this back-reference failing?\n\necho 'ba' | grep -E '(a)\\1|b\\1'\n\nThis outputs an error message, because the second '\\1' has nothing\nto refer back to, meaning it will never match anything.\n\n14. How can I match across lines?\n\nStandard grep cannot do this, as it is fundamentally line-based.\nTherefore, merely using the '[:space:]' character class does not\nmatch newlines in the way you might expect.\n\nWith the GNU 'grep' option '-z' ('--null-data'), each input and\noutput \"line\" is null-terminated; *note Other Options::. Thus, you\ncan match newlines in the input, but typically if there is a match\nthe entire input is output, so this usage is often combined with\noutput-suppressing options like '-q', e.g.:\n\nprintf 'foo\\nbar\\n' | grep -z -q 'foo[[:space:]]\\+bar'\n\nIf this does not suffice, you can transform the input before giving\nit to 'grep', or turn to 'awk', 'sed', 'perl', or many other\nutilities that are designed to operate across lines.\n\n15. What do 'grep', 'fgrep', and 'egrep' stand for?\n\nThe name 'grep' comes from the way line editing was done on Unix.\nFor example, 'ed' uses the following syntax to print a list of\nmatching lines on the screen:\n\nglobal/regular expression/print\ng/re/p\n\n'fgrep' stands for Fixed 'grep'; 'egrep' stands for Extended\n'grep'.\n\nFile: grep.info, Node: Performance, Next: Reporting Bugs, Prev: Usage, Up: Top\n", "subsections": [] }, "5 Performance": { "content": "Typically 'grep' is an efficient way to search text. However, it can be\nquite slow in some cases, and it can search large files where even minor\nperformance tweaking can help significantly. Although the algorithm\nused by 'grep' is an implementation detail that can change from release\nto release, understanding its basic strengths and weaknesses can help\nyou improve its performance.\n\nThe 'grep' command operates partly via a set of automata that are\ndesigned for efficiency, and partly via a slower matcher that takes over\nwhen the fast matchers run into unusual features like back-references.\nWhen feasible, the Boyer-Moore fast string searching algorithm is used\nto match a single fixed pattern, and the Aho-Corasick algorithm is used\nto match multiple fixed patterns.\n\nGenerally speaking 'grep' operates more efficiently in single-byte\nlocales, since it can avoid the special processing needed for multi-byte\ncharacters. If your patterns will work just as well that way, setting\n'LCALL' to a single-byte locale can help performance considerably.\nSetting 'LCALL='C'' can be particularly efficient, as 'grep' is tuned\nfor that locale.\n\nOutside the 'C' locale, case-insensitive search, and search for\nbracket expressions like '[a-z]' and '[[=a=]b]', can be surprisingly\ninefficient due to difficulties in fast portable access to concepts like\nmulti-character collating elements.\n\nA back-reference such as '\\1' can hurt performance significantly in\nsome cases, since back-references cannot in general be implemented via a\nfinite state automaton, and instead trigger a backtracking algorithm\nthat can be quite inefficient. For example, although the pattern\n'^(.*)\\1{14}(.*)\\2{13}$' matches only lines whose lengths can be written\nas a sum 15x + 14y for nonnegative integers x and y, the pattern matcher\ndoes not perform linear Diophantine analysis and instead backtracks\nthrough all possible matching strings, using an algorithm that is\nexponential in the worst case.\n\nOn some operating systems that support files with holes--large regions\nof zeros that are not physically present on secondary storage--'grep' can\nskip over the holes efficiently without needing to read the zeros. This\noptimization is not available if the '-a' ('--binary-files=text') option\nis used (*note File and Directory Selection::), unless the '-z'\n('--null-data') option is also used (*note Other Options::).\n\nFor more about the algorithms used by 'grep' and about related string\nmatching algorithms, see:\n\n* Aho AV. Algorithms for finding patterns in strings. In: van Leeuwen\nJ. Handbook of Theoretical Computer Science, vol. A. New York:\nElsevier; 1990. p. 255-300. This surveys classic string matching\nalgorithms, some of which are used by 'grep'.\n\n* Aho AV, Corasick MJ. Efficient string matching: an aid to\nbibliographic search. CACM. 1975;18(6):333-40.\n. This introduces the\nAho-Corasick algorithm.\n\n* Boyer RS, Moore JS. A fast string searching algorithm. CACM.\n1977;20(10):762-72. .\nThis introduces the Boyer-Moore algorithm.\n\n* Faro S, Lecroq T. The exact online string matching problem: a\nreview of the most recent results. ACM Comput Surv.\n2013;45(2):13. . This\nsurveys string matching algorithms that might help improve the\nperformance of 'grep' in the future.\n\nFile: grep.info, Node: Reporting Bugs, Next: Copying, Prev: Performance, Up: Top\n", "subsections": [] }, "6 Reporting bugs": { "content": "Bug reports can be found at the GNU bug report logs for 'grep'\n(https://debbugs.gnu.org/cgi/pkgreport.cgi?package=grep). If you find a\nbug not listed there, please email it to to create a\nnew bug report.\n\n* Menu:\n\n* Known Bugs::\n\nFile: grep.info, Node: Known Bugs, Up: Reporting Bugs\n", "subsections": [ { "name": "6.1 Known Bugs", "content": "Large repetition counts in the '{n,m}' construct may cause 'grep' to use\nlots of memory. In addition, certain other obscure regular expressions\nrequire exponential time and space, and may cause 'grep' to run out of\nmemory.\n\nBack-references can greatly slow down matching, as they can generate\nexponentially many matching possibilities that can consume both time and\nmemory to explore. Also, the POSIX specification for back-references is\nat times unclear. Furthermore, many regular expression implementations\nhave back-reference bugs that can cause programs to return incorrect\nanswers or even crash, and fixing these bugs has often been\nlow-priority: for example, as of 2021 the GNU C library bug database\n(https://sourceware.org/bugzilla/) contained back-reference bugs 52,\n10844, 11053, 24269 and 25322, with little sign of forthcoming fixes.\nLuckily, back-references are rarely useful and it should be little\ntrouble to avoid them in practical applications.\n\nFile: grep.info, Node: Copying, Next: Index, Prev: Reporting Bugs, Up: Top\n" } ] }, "7 Copying": { "content": "GNU 'grep' is licensed under the GNU GPL, which makes it \"free\nsoftware\".\n\nThe \"free\" in \"free software\" refers to liberty, not price. As some\nGNU project advocates like to point out, think of \"free speech\" rather\nthan \"free beer\". In short, you have the right (freedom) to run and\nchange 'grep' and distribute it to other people, and--if you want--charge\nmoney for doing either. The important restriction is that you have to\ngrant your recipients the same rights and impose the same restrictions.\n\nThis general method of licensing software is sometimes called \"open\nsource\". The GNU project prefers the term \"free software\" for reasons\noutlined at\n.\n\nThis manual is free documentation in the same sense. The\ndocumentation license is included below. The license for the program is\navailable with the source code, or at\n.\n\n* Menu:\n\n* GNU Free Documentation License::\n\nFile: grep.info, Node: GNU Free Documentation License, Up: Copying\n", "subsections": [ { "name": "7.1 GNU Free Documentation License", "content": "Version 1.3, 3 November 2008\n\nCopyright (C) 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc.\n\n\nEveryone is permitted to copy and distribute verbatim copies\nof this license document, but changing it is not allowed.\n\n0. PREAMBLE\n\nThe purpose of this License is to make a manual, textbook, or other\nfunctional and useful document \"free\" in the sense of freedom: to\nassure everyone the effective freedom to copy and redistribute it,\nwith or without modifying it, either commercially or\nnoncommercially. Secondarily, this License preserves for the\nauthor and publisher a way to get credit for their work, while not\nbeing considered responsible for modifications made by others.\n\nThis License is a kind of \"copyleft\", which means that derivative\nworks of the document must themselves be free in the same sense.\nIt complements the GNU General Public License, which is a copyleft\nlicense designed for free software.\n\nWe have designed this License in order to use it for manuals for\nfree software, because free software needs free documentation: a\nfree program should come with manuals providing the same freedoms\nthat the software does. But this License is not limited to\nsoftware manuals; it can be used for any textual work, regardless\nof subject matter or whether it is published as a printed book. We\nrecommend this License principally for works whose purpose is\ninstruction or reference.\n\n1. APPLICABILITY AND DEFINITIONS\n\nThis License applies to any manual or other work, in any medium,\nthat contains a notice placed by the copyright holder saying it can\nbe distributed under the terms of this License. Such a notice\ngrants a world-wide, royalty-free license, unlimited in duration,\nto use that work under the conditions stated herein. The\n\"Document\", below, refers to any such manual or work. Any member\nof the public is a licensee, and is addressed as \"you\". You accept\nthe license if you copy, modify or distribute the work in a way\nrequiring permission under copyright law.\n\nA \"Modified Version\" of the Document means any work containing the\nDocument or a portion of it, either copied verbatim, or with\nmodifications and/or translated into another language.\n\nA \"Secondary Section\" is a named appendix or a front-matter section\nof the Document that deals exclusively with the relationship of the\npublishers or authors of the Document to the Document's overall\nsubject (or to related matters) and contains nothing that could\nfall directly within that overall subject. (Thus, if the Document\nis in part a textbook of mathematics, a Secondary Section may not\nexplain any mathematics.) The relationship could be a matter of\nhistorical connection with the subject or with related matters, or\nof legal, commercial, philosophical, ethical or political position\nregarding them.\n\nThe \"Invariant Sections\" are certain Secondary Sections whose\ntitles are designated, as being those of Invariant Sections, in the\nnotice that says that the Document is released under this License.\nIf a section does not fit the above definition of Secondary then it\nis not allowed to be designated as Invariant. The Document may\ncontain zero Invariant Sections. If the Document does not identify\nany Invariant Sections then there are none.\n\nThe \"Cover Texts\" are certain short passages of text that are\nlisted, as Front-Cover Texts or Back-Cover Texts, in the notice\nthat says that the Document is released under this License. A\nFront-Cover Text may be at most 5 words, and a Back-Cover Text may\nbe at most 25 words.\n\nA \"Transparent\" copy of the Document means a machine-readable copy,\nrepresented in a format whose specification is available to the\ngeneral public, that is suitable for revising the document\nstraightforwardly with generic text editors or (for images composed\nof pixels) generic paint programs or (for drawings) some widely\navailable drawing editor, and that is suitable for input to text\nformatters or for automatic translation to a variety of formats\nsuitable for input to text formatters. A copy made in an otherwise\nTransparent file format whose markup, or absence of markup, has\nbeen arranged to thwart or discourage subsequent modification by\nreaders is not Transparent. An image format is not Transparent if\nused for any substantial amount of text. A copy that is not\n\"Transparent\" is called \"Opaque\".\n\nExamples of suitable formats for Transparent copies include plain\nASCII without markup, Texinfo input format, LaTeX input format,\nSGML or XML using a publicly available DTD, and standard-conforming\nsimple HTML, PostScript or PDF designed for human modification.\nExamples of transparent image formats include PNG, XCF and JPG.\nOpaque formats include proprietary formats that can be read and\nedited only by proprietary word processors, SGML or XML for which\nthe DTD and/or processing tools are not generally available, and\nthe machine-generated HTML, PostScript or PDF produced by some word\nprocessors for output purposes only.\n\nThe \"Title Page\" means, for a printed book, the title page itself,\nplus such following pages as are needed to hold, legibly, the\nmaterial this License requires to appear in the title page. For\nworks in formats which do not have any title page as such, \"Title\nPage\" means the text near the most prominent appearance of the\nwork's title, preceding the beginning of the body of the text.\n\nThe \"publisher\" means any person or entity that distributes copies\nof the Document to the public.\n\nA section \"Entitled XYZ\" means a named subunit of the Document\nwhose title either is precisely XYZ or contains XYZ in parentheses\nfollowing text that translates XYZ in another language. (Here XYZ\nstands for a specific section name mentioned below, such as\n\"Acknowledgements\", \"Dedications\", \"Endorsements\", or \"History\".)\nTo \"Preserve the Title\" of such a section when you modify the\nDocument means that it remains a section \"Entitled XYZ\" according\nto this definition.\n\nThe Document may include Warranty Disclaimers next to the notice\nwhich states that this License applies to the Document. These\nWarranty Disclaimers are considered to be included by reference in\nthis License, but only as regards disclaiming warranties: any other\nimplication that these Warranty Disclaimers may have is void and\nhas no effect on the meaning of this License.\n\n2. VERBATIM COPYING\n\nYou may copy and distribute the Document in any medium, either\ncommercially or noncommercially, provided that this License, the\ncopyright notices, and the license notice saying this License\napplies to the Document are reproduced in all copies, and that you\nadd no other conditions whatsoever to those of this License. You\nmay not use technical measures to obstruct or control the reading\nor further copying of the copies you make or distribute. However,\nyou may accept compensation in exchange for copies. If you\ndistribute a large enough number of copies you must also follow the\nconditions in section 3.\n\nYou may also lend copies, under the same conditions stated above,\nand you may publicly display copies.\n\n3. COPYING IN QUANTITY\n\nIf you publish printed copies (or copies in media that commonly\nhave printed covers) of the Document, numbering more than 100, and\nthe Document's license notice requires Cover Texts, you must\nenclose the copies in covers that carry, clearly and legibly, all\nthese Cover Texts: Front-Cover Texts on the front cover, and\nBack-Cover Texts on the back cover. Both covers must also clearly\nand legibly identify you as the publisher of these copies. The\nfront cover must present the full title with all words of the title\nequally prominent and visible. You may add other material on the\ncovers in addition. Copying with changes limited to the covers, as\nlong as they preserve the title of the Document and satisfy these\nconditions, can be treated as verbatim copying in other respects.\n\nIf the required texts for either cover are too voluminous to fit\nlegibly, you should put the first ones listed (as many as fit\nreasonably) on the actual cover, and continue the rest onto\nadjacent pages.\n\nIf you publish or distribute Opaque copies of the Document\nnumbering more than 100, you must either include a machine-readable\nTransparent copy along with each Opaque copy, or state in or with\neach Opaque copy a computer-network location from which the general\nnetwork-using public has access to download using public-standard\nnetwork protocols a complete Transparent copy of the Document, free\nof added material. If you use the latter option, you must take\nreasonably prudent steps, when you begin distribution of Opaque\ncopies in quantity, to ensure that this Transparent copy will\nremain thus accessible at the stated location until at least one\nyear after the last time you distribute an Opaque copy (directly or\nthrough your agents or retailers) of that edition to the public.\n\nIt is requested, but not required, that you contact the authors of\nthe Document well before redistributing any large number of copies,\nto give them a chance to provide you with an updated version of the\nDocument.\n\n4. MODIFICATIONS\n\nYou may copy and distribute a Modified Version of the Document\nunder the conditions of sections 2 and 3 above, provided that you\nrelease the Modified Version under precisely this License, with the\nModified Version filling the role of the Document, thus licensing\ndistribution and modification of the Modified Version to whoever\npossesses a copy of it. In addition, you must do these things in\nthe Modified Version:\n\nA. Use in the Title Page (and on the covers, if any) a title\ndistinct from that of the Document, and from those of previous\nversions (which should, if there were any, be listed in the\nHistory section of the Document). You may use the same title\nas a previous version if the original publisher of that\nversion gives permission.\n\nB. List on the Title Page, as authors, one or more persons or\nentities responsible for authorship of the modifications in\nthe Modified Version, together with at least five of the\nprincipal authors of the Document (all of its principal\nauthors, if it has fewer than five), unless they release you\nfrom this requirement.\n\nC. State on the Title page the name of the publisher of the\nModified Version, as the publisher.\n\nD. Preserve all the copyright notices of the Document.\n\nE. Add an appropriate copyright notice for your modifications\nadjacent to the other copyright notices.\n\nF. Include, immediately after the copyright notices, a license\nnotice giving the public permission to use the Modified\nVersion under the terms of this License, in the form shown in\nthe Addendum below.\n\nG. Preserve in that license notice the full lists of Invariant\nSections and required Cover Texts given in the Document's\nlicense notice.\n\nH. Include an unaltered copy of this License.\n\nI. Preserve the section Entitled \"History\", Preserve its Title,\nand add to it an item stating at least the title, year, new\nauthors, and publisher of the Modified Version as given on the\nTitle Page. If there is no section Entitled \"History\" in the\nDocument, create one stating the title, year, authors, and\npublisher of the Document as given on its Title Page, then add\nan item describing the Modified Version as stated in the\nprevious sentence.\n\nJ. Preserve the network location, if any, given in the Document\nfor public access to a Transparent copy of the Document, and\nlikewise the network locations given in the Document for\nprevious versions it was based on. These may be placed in the\n\"History\" section. You may omit a network location for a work\nthat was published at least four years before the Document\nitself, or if the original publisher of the version it refers\nto gives permission.\n\nK. For any section Entitled \"Acknowledgements\" or \"Dedications\",\nPreserve the Title of the section, and preserve in the section\nall the substance and tone of each of the contributor\nacknowledgements and/or dedications given therein.\n\nL. Preserve all the Invariant Sections of the Document, unaltered\nin their text and in their titles. Section numbers or the\nequivalent are not considered part of the section titles.\n\nM. Delete any section Entitled \"Endorsements\". Such a section\nmay not be included in the Modified Version.\n\nN. Do not retitle any existing section to be Entitled\n\"Endorsements\" or to conflict in title with any Invariant\nSection.\n\nO. Preserve any Warranty Disclaimers.\n\nIf the Modified Version includes new front-matter sections or\nappendices that qualify as Secondary Sections and contain no\nmaterial copied from the Document, you may at your option designate\nsome or all of these sections as invariant. To do this, add their\ntitles to the list of Invariant Sections in the Modified Version's\nlicense notice. These titles must be distinct from any other\nsection titles.\n\nYou may add a section Entitled \"Endorsements\", provided it contains\nnothing but endorsements of your Modified Version by various\nparties--for example, statements of peer review or that the text has\nbeen approved by an organization as the authoritative definition of\na standard.\n\nYou may add a passage of up to five words as a Front-Cover Text,\nand a passage of up to 25 words as a Back-Cover Text, to the end of\nthe list of Cover Texts in the Modified Version. Only one passage\nof Front-Cover Text and one of Back-Cover Text may be added by (or\nthrough arrangements made by) any one entity. If the Document\nalready includes a cover text for the same cover, previously added\nby you or by arrangement made by the same entity you are acting on\nbehalf of, you may not add another; but you may replace the old\none, on explicit permission from the previous publisher that added\nthe old one.\n\nThe author(s) and publisher(s) of the Document do not by this\nLicense give permission to use their names for publicity for or to\nassert or imply endorsement of any Modified Version.\n\n5. COMBINING DOCUMENTS\n\nYou may combine the Document with other documents released under\nthis License, under the terms defined in section 4 above for\nmodified versions, provided that you include in the combination all\nof the Invariant Sections of all of the original documents,\nunmodified, and list them all as Invariant Sections of your\ncombined work in its license notice, and that you preserve all\ntheir Warranty Disclaimers.\n\nThe combined work need only contain one copy of this License, and\nmultiple identical Invariant Sections may be replaced with a single\ncopy. If there are multiple Invariant Sections with the same name\nbut different contents, make the title of each such section unique\nby adding at the end of it, in parentheses, the name of the\noriginal author or publisher of that section if known, or else a\nunique number. Make the same adjustment to the section titles in\nthe list of Invariant Sections in the license notice of the\ncombined work.\n\nIn the combination, you must combine any sections Entitled\n\"History\" in the various original documents, forming one section\nEntitled \"History\"; likewise combine any sections Entitled\n\"Acknowledgements\", and any sections Entitled \"Dedications\". You\nmust delete all sections Entitled \"Endorsements.\"\n\n6. COLLECTIONS OF DOCUMENTS\n\nYou may make a collection consisting of the Document and other\ndocuments released under this License, and replace the individual\ncopies of this License in the various documents with a single copy\nthat is included in the collection, provided that you follow the\nrules of this License for verbatim copying of each of the documents\nin all other respects.\n\nYou may extract a single document from such a collection, and\ndistribute it individually under this License, provided you insert\na copy of this License into the extracted document, and follow this\nLicense in all other respects regarding verbatim copying of that\ndocument.\n\n7. AGGREGATION WITH INDEPENDENT WORKS\n\nA compilation of the Document or its derivatives with other\nseparate and independent documents or works, in or on a volume of a\nstorage or distribution medium, is called an \"aggregate\" if the\ncopyright resulting from the compilation is not used to limit the\nlegal rights of the compilation's users beyond what the individual\nworks permit. When the Document is included in an aggregate, this\nLicense does not apply to the other works in the aggregate which\nare not themselves derivative works of the Document.\n\nIf the Cover Text requirement of section 3 is applicable to these\ncopies of the Document, then if the Document is less than one half\nof the entire aggregate, the Document's Cover Texts may be placed\non covers that bracket the Document within the aggregate, or the\nelectronic equivalent of covers if the Document is in electronic\nform. Otherwise they must appear on printed covers that bracket\nthe whole aggregate.\n\n8. TRANSLATION\n\nTranslation is considered a kind of modification, so you may\ndistribute translations of the Document under the terms of section\n4. Replacing Invariant Sections with translations requires special\npermission from their copyright holders, but you may include\ntranslations of some or all Invariant Sections in addition to the\noriginal versions of these Invariant Sections. You may include a\ntranslation of this License, and all the license notices in the\nDocument, and any Warranty Disclaimers, provided that you also\ninclude the original English version of this License and the\noriginal versions of those notices and disclaimers. In case of a\ndisagreement between the translation and the original version of\nthis License or a notice or disclaimer, the original version will\nprevail.\n\nIf a section in the Document is Entitled \"Acknowledgements\",\n\"Dedications\", or \"History\", the requirement (section 4) to\nPreserve its Title (section 1) will typically require changing the\nactual title.\n\n9. TERMINATION\n\nYou may not copy, modify, sublicense, or distribute the Document\nexcept as expressly provided under this License. Any attempt\notherwise to copy, modify, sublicense, or distribute it is void,\nand will automatically terminate your rights under this License.\n\nHowever, if you cease all violation of this License, then your\nlicense from a particular copyright holder is reinstated (a)\nprovisionally, unless and until the copyright holder explicitly and\nfinally terminates your license, and (b) permanently, if the\ncopyright holder fails to notify you of the violation by some\nreasonable means prior to 60 days after the cessation.\n\nMoreover, your license from a particular copyright holder is\nreinstated permanently if the copyright holder notifies you of the\nviolation by some reasonable means, this is the first time you have\nreceived notice of violation of this License (for any work) from\nthat copyright holder, and you cure the violation prior to 30 days\nafter your receipt of the notice.\n\nTermination of your rights under this section does not terminate\nthe licenses of parties who have received copies or rights from you\nunder this License. If your rights have been terminated and not\npermanently reinstated, receipt of a copy of some or all of the\nsame material does not give you any rights to use it.\n\n10. FUTURE REVISIONS OF THIS LICENSE\n\nThe Free Software Foundation may publish new, revised versions of\nthe GNU Free Documentation License from time to time. Such new\nversions will be similar in spirit to the present version, but may\ndiffer in detail to address new problems or concerns. See\n.\n\nEach version of the License is given a distinguishing version\nnumber. If the Document specifies that a particular numbered\nversion of this License \"or any later version\" applies to it, you\nhave the option of following the terms and conditions either of\nthat specified version or of any later version that has been\npublished (not as a draft) by the Free Software Foundation. If the\nDocument does not specify a version number of this License, you may\nchoose any version ever published (not as a draft) by the Free\nSoftware Foundation. If the Document specifies that a proxy can\ndecide which future versions of this License can be used, that\nproxy's public statement of acceptance of a version permanently\nauthorizes you to choose that version for the Document.\n\n11. RELICENSING\n\n\"Massive Multiauthor Collaboration Site\" (or \"MMC Site\") means any\nWorld Wide Web server that publishes copyrightable works and also\nprovides prominent facilities for anybody to edit those works. A\npublic wiki that anybody can edit is an example of such a server.\nA \"Massive Multiauthor Collaboration\" (or \"MMC\") contained in the\nsite means any set of copyrightable works thus published on the MMC\nsite.\n\n\"CC-BY-SA\" means the Creative Commons Attribution-Share Alike 3.0\nlicense published by Creative Commons Corporation, a not-for-profit\ncorporation with a principal place of business in San Francisco,\nCalifornia, as well as future copyleft versions of that license\npublished by that same organization.\n\n\"Incorporate\" means to publish or republish a Document, in whole or\nin part, as part of another Document.\n\nAn MMC is \"eligible for relicensing\" if it is licensed under this\nLicense, and if all works that were first published under this\nLicense somewhere other than this MMC, and subsequently\nincorporated in whole or in part into the MMC, (1) had no cover\ntexts or invariant sections, and (2) were thus incorporated prior\nto November 1, 2008.\n\nThe operator of an MMC Site may republish an MMC contained in the\nsite under CC-BY-SA on the same site at any time before August 1,\n2009, provided the MMC is eligible for relicensing.\n" }, { "name": "ADDENDUM: How to use this License for your documents", "content": "To use this License in a document you have written, include a copy of\nthe License in the document and put the following copyright and license\nnotices just after the title page:\n\nCopyright (C) YEAR YOUR NAME.\nPermission is granted to copy, distribute and/or modify this document\nunder the terms of the GNU Free Documentation License, Version 1.3\nor any later version published by the Free Software Foundation;\nwith no Invariant Sections, no Front-Cover Texts, and no Back-Cover\nTexts. A copy of the license is included in the section entitled ``GNU\nFree Documentation License''.\n\nIf you have Invariant Sections, Front-Cover Texts and Back-Cover\nTexts, replace the \"with...Texts.\" line with this:\n\nwith the Invariant Sections being LIST THEIR TITLES, with\nthe Front-Cover Texts being LIST, and with the Back-Cover Texts\nbeing LIST.\n\nIf you have Invariant Sections without Cover Texts, or some other\ncombination of the three, merge those two alternatives to suit the\nsituation.\n\nIf your document contains nontrivial examples of program code, we\nrecommend releasing these examples in parallel under your choice of free\nsoftware license, such as the GNU General Public License, to permit\ntheir use in free software.\n\nFile: grep.info, Node: Index, Prev: Copying, Up: Top\n" } ] }, "Index": { "content": "* Menu:\n\n* *: Fundamental Structure.\n(line 22)\n* +: Fundamental Structure.\n(line 25)\n* --: Other Options. (line 7)\n* --after-context: Context Line Control.\n(line 15)\n* --basic-regexp: grep Programs. (line 15)\n* --before-context: Context Line Control.\n(line 19)\n* --binary: Other Options. (line 22)\n* --binary-files: File and Directory Selection.\n(line 12)\n* --byte-offset: Output Line Prefix Control.\n(line 12)\n* --color: General Output Control.\n(line 14)\n* --colour: General Output Control.\n(line 14)\n* --context: Context Line Control.\n(line 24)\n* --count: General Output Control.\n(line 8)\n* --dereference-recursive: File and Directory Selection.\n(line 113)\n* --devices: File and Directory Selection.\n(line 51)\n* --directories: File and Directory Selection.\n(line 62)\n* --exclude: File and Directory Selection.\n(line 73)\n* --exclude-dir: File and Directory Selection.\n(line 87)\n* --exclude-from: File and Directory Selection.\n(line 83)\n* --extended-regexp: grep Programs. (line 20)\n* --file: Matching Control. (line 17)\n* --files-with-matches: General Output Control.\n(line 34)\n* --files-without-match: General Output Control.\n(line 29)\n* --fixed-strings: grep Programs. (line 25)\n* --group-separator: Context Line Control.\n(line 27)\n* --group-separator <1>: Context Line Control.\n(line 31)\n* --help: Generic Program Information.\n(line 7)\n* --ignore-case: Matching Control. (line 26)\n* --include: File and Directory Selection.\n(line 97)\n* --initial-tab: Output Line Prefix Control.\n(line 41)\n* --invert-match: Matching Control. (line 51)\n* --label: Output Line Prefix Control.\n(line 28)\n* --line-buffered: Other Options. (line 13)\n* --line-number: Output Line Prefix Control.\n(line 36)\n* --line-regexp: Matching Control. (line 73)\n* --max-count: General Output Control.\n(line 40)\n* --no-filename: Output Line Prefix Control.\n(line 23)\n* --no-ignore-case: Matching Control. (line 44)\n* --no-messages: General Output Control.\n(line 85)\n* --null: Output Line Prefix Control.\n(line 50)\n* --null-data: Other Options. (line 43)\n* --only-matching: General Output Control.\n(line 70)\n* --perl-regexp: grep Programs. (line 30)\n* --quiet: General Output Control.\n(line 78)\n* --recursive: File and Directory Selection.\n(line 105)\n* --regexp=PATTERNS: Matching Control. (line 8)\n* --silent: General Output Control.\n(line 78)\n* --text: File and Directory Selection.\n(line 8)\n* --version: Generic Program Information.\n(line 12)\n* --with-filename: Output Line Prefix Control.\n(line 18)\n* --word-regexp: Matching Control. (line 56)\n* -A: Context Line Control.\n(line 15)\n* -a: File and Directory Selection.\n(line 8)\n* -b: Output Line Prefix Control.\n(line 12)\n* -B: Context Line Control.\n(line 19)\n* -c: General Output Control.\n(line 8)\n* -C: Context Line Control.\n(line 24)\n* -D: File and Directory Selection.\n(line 51)\n* -d: File and Directory Selection.\n(line 62)\n* -e: Matching Control. (line 8)\n* -E: grep Programs. (line 20)\n* -f: Matching Control. (line 17)\n* -F: grep Programs. (line 25)\n* -G: grep Programs. (line 15)\n* -H: Output Line Prefix Control.\n(line 18)\n* -h: Output Line Prefix Control.\n(line 23)\n* -i: Matching Control. (line 26)\n* -L: General Output Control.\n(line 29)\n* -l: General Output Control.\n(line 34)\n* -m: General Output Control.\n(line 40)\n* -n: Output Line Prefix Control.\n(line 36)\n* -NUM: Context Line Control.\n(line 24)\n* -o: General Output Control.\n(line 70)\n* -P: grep Programs. (line 30)\n* -q: General Output Control.\n(line 78)\n* -r: File and Directory Selection.\n(line 105)\n* -R: File and Directory Selection.\n(line 113)\n* -s: General Output Control.\n(line 85)\n* -T: Output Line Prefix Control.\n(line 41)\n* -U: Other Options. (line 22)\n* -V: Generic Program Information.\n(line 12)\n* -v: Matching Control. (line 51)\n* -w: Matching Control. (line 56)\n* -x: Matching Control. (line 73)\n* -y: Matching Control. (line 26)\n* -Z: Output Line Prefix Control.\n(line 50)\n* -z: Other Options. (line 43)\n* .: Fundamental Structure.\n(line 11)\n* ?: Fundamental Structure.\n(line 19)\n* NGNUnonoptionargvflags environment variable: Environment Variables.\n(line 178)\n* {,M}: Fundamental Structure.\n(line 34)\n* {N,M}: Fundamental Structure.\n(line 38)\n* {N,}: Fundamental Structure.\n(line 31)\n* {N}: Fundamental Structure.\n(line 28)\n* after context: Context Line Control.\n(line 15)\n* alnum character class: Character Classes and Bracket Expressions.\n(line 31)\n* alpha character class: Character Classes and Bracket Expressions.\n(line 36)\n* alphabetic characters: Character Classes and Bracket Expressions.\n(line 36)\n* alphanumeric characters: Character Classes and Bracket Expressions.\n(line 31)\n* anchoring: Anchoring. (line 6)\n* asterisk: Fundamental Structure.\n(line 22)\n* back-reference: Back-references and Subexpressions.\n(line 6)\n* back-references: Performance. (line 32)\n* backslash: The Backslash Character and Special Expressions.\n(line 6)\n* basic regular expressions: Basic vs Extended. (line 6)\n* before context: Context Line Control.\n(line 19)\n* binary files: File and Directory Selection.\n(line 8)\n* binary files <1>: File and Directory Selection.\n(line 12)\n* binary I/O: Other Options. (line 22)\n* blank character class: Character Classes and Bracket Expressions.\n(line 41)\n* blank characters: Character Classes and Bracket Expressions.\n(line 41)\n* bn GREPCOLORS capability: Environment Variables.\n(line 121)\n* braces, first argument omitted: Fundamental Structure.\n(line 34)\n* braces, one argument: Fundamental Structure.\n(line 28)\n* braces, second argument omitted: Fundamental Structure.\n(line 31)\n* braces, two arguments: Fundamental Structure.\n(line 38)\n* bracket expression: Character Classes and Bracket Expressions.\n(line 6)\n* Bugs, known: Known Bugs. (line 6)\n* bugs, reporting: Reporting Bugs. (line 6)\n* byte offset: Output Line Prefix Control.\n(line 12)\n* case insensitive search: Matching Control. (line 26)\n* case insensitive search <1>: Performance. (line 27)\n* changing name of standard input: Output Line Prefix Control.\n(line 28)\n* character class: Character Classes and Bracket Expressions.\n(line 6)\n* character classes: Character Classes and Bracket Expressions.\n(line 30)\n* character encoding: Character Encoding. (line 6)\n* character type: Environment Variables.\n(line 148)\n* classes of characters: Character Classes and Bracket Expressions.\n(line 30)\n* cntrl character class: Character Classes and Bracket Expressions.\n(line 44)\n* context lines: General Output Control.\n(line 62)\n* context lines <1>: Context Line Control.\n(line 6)\n* context lines <2>: Context Line Control.\n(line 24)\n* context lines, after match: Context Line Control.\n(line 15)\n* context lines, before match: Context Line Control.\n(line 19)\n* control characters: Character Classes and Bracket Expressions.\n(line 44)\n* copying: Copying. (line 6)\n* counting lines: General Output Control.\n(line 8)\n* cx GREPCOLORS capability: Environment Variables.\n(line 72)\n* device search: File and Directory Selection.\n(line 51)\n* digit character class: Character Classes and Bracket Expressions.\n(line 49)\n* digit characters: Character Classes and Bracket Expressions.\n(line 49)\n* directory search: File and Directory Selection.\n(line 62)\n* dot: Fundamental Structure.\n(line 11)\n* encoding error: Environment Variables.\n(line 155)\n* environment variables: Environment Variables.\n(line 44)\n* exclude directories: File and Directory Selection.\n(line 87)\n* exclude files: File and Directory Selection.\n(line 73)\n* exclude files <1>: File and Directory Selection.\n(line 83)\n* exit status: Exit Status. (line 6)\n* FAQ about grep usage: Usage. (line 32)\n* files which don't match: General Output Control.\n(line 29)\n* fn GREPCOLORS capability: Environment Variables.\n(line 111)\n* fn GREPCOLORS capability <1>: Environment Variables.\n(line 126)\n* graph character class: Character Classes and Bracket Expressions.\n(line 52)\n* graphic characters: Character Classes and Bracket Expressions.\n(line 52)\n* grep programs: grep Programs. (line 6)\n* GREPCOLOR environment variable: Environment Variables.\n(line 45)\n* GREPCOLORS environment variable: Environment Variables.\n(line 56)\n* group separator: Context Line Control.\n(line 27)\n* group separator <1>: Context Line Control.\n(line 31)\n* hexadecimal digits: Character Classes and Bracket Expressions.\n(line 76)\n* highlight markers: Environment Variables.\n(line 45)\n* highlight markers <1>: Environment Variables.\n(line 56)\n* highlight, color, colour: General Output Control.\n(line 14)\n* holes in files: Performance. (line 42)\n* include files: File and Directory Selection.\n(line 97)\n* interval expressions: Fundamental Structure.\n(line 14)\n* interval expressions <1>: Basic vs Extended. (line 27)\n* invert matching: Matching Control. (line 51)\n* LANG environment variable: Environment Variables.\n(line 9)\n* LANG environment variable <1>: Environment Variables.\n(line 148)\n* LANG environment variable <2>: Environment Variables.\n(line 155)\n* LANG environment variable <3>: Environment Variables.\n(line 164)\n* LANGUAGE environment variable: Environment Variables.\n(line 9)\n* LANGUAGE environment variable <1>: Environment Variables.\n(line 164)\n* language of messages: Environment Variables.\n(line 164)\n* LCALL environment variable: Environment Variables.\n(line 9)\n* LCALL environment variable <1>: Environment Variables.\n(line 148)\n* LCALL environment variable <2>: Environment Variables.\n(line 155)\n* LCALL environment variable <3>: Environment Variables.\n(line 164)\n* LCCOLLATE environment variable: Environment Variables.\n(line 148)\n* LCCTYPE environment variable: Environment Variables.\n(line 155)\n* LCMESSAGES environment variable: Environment Variables.\n(line 9)\n* LCMESSAGES environment variable <1>: Environment Variables.\n(line 164)\n* line buffering: Other Options. (line 13)\n* line numbering: Output Line Prefix Control.\n(line 36)\n* ln GREPCOLORS capability: Environment Variables.\n(line 116)\n* locales: Performance. (line 20)\n* lower character class: Character Classes and Bracket Expressions.\n(line 55)\n* lower-case letters: Character Classes and Bracket Expressions.\n(line 55)\n* match expression at most M times: Fundamental Structure.\n(line 34)\n* match expression at most once: Fundamental Structure.\n(line 19)\n* match expression from N to M times: Fundamental Structure.\n(line 38)\n* match expression N or more times: Fundamental Structure.\n(line 31)\n* match expression N times: Fundamental Structure.\n(line 28)\n* match expression one or more times: Fundamental Structure.\n(line 25)\n* match expression zero or more times: Fundamental Structure.\n(line 22)\n* match the whole line: Matching Control. (line 73)\n* matching basic regular expressions: grep Programs. (line 15)\n* matching extended regular expressions: grep Programs. (line 20)\n* matching fixed strings: grep Programs. (line 25)\n* matching Perl-compatible regular expressions: grep Programs.\n(line 30)\n* matching whole words: Matching Control. (line 56)\n* max-count: General Output Control.\n(line 40)\n* mc GREPCOLORS capability: Environment Variables.\n(line 103)\n* message language: Environment Variables.\n(line 164)\n* ms GREPCOLORS capability: Environment Variables.\n(line 95)\n* MS-Windows binary I/O: Other Options. (line 22)\n* mt GREPCOLORS capability: Environment Variables.\n(line 87)\n* names of matching files: General Output Control.\n(line 34)\n* national language support: Environment Variables.\n(line 148)\n* national language support <1>: Environment Variables.\n(line 164)\n* ne GREPCOLORS capability: Environment Variables.\n(line 133)\n* NLS: Environment Variables.\n(line 148)\n* no filename prefix: Output Line Prefix Control.\n(line 23)\n* non-ASCII matching: Matching Non-ASCII. (line 6)\n* non-printable matching: Matching Non-ASCII. (line 6)\n* null character: Environment Variables.\n(line 155)\n* numeric characters: Character Classes and Bracket Expressions.\n(line 49)\n* only matching: General Output Control.\n(line 70)\n* option delimiter: Other Options. (line 7)\n* ordinary characters: Fundamental Structure.\n(line 6)\n* patterns from file: Matching Control. (line 17)\n* patterns option: Matching Control. (line 8)\n* performance: Performance. (line 6)\n* period: Fundamental Structure.\n(line 11)\n* plus sign: Fundamental Structure.\n(line 25)\n* POSIXLYCORRECT environment variable: Environment Variables.\n(line 169)\n* print character class: Character Classes and Bracket Expressions.\n(line 59)\n* print non-matching lines: Matching Control. (line 51)\n* printable characters: Character Classes and Bracket Expressions.\n(line 59)\n* punct character class: Character Classes and Bracket Expressions.\n(line 62)\n* punctuation characters: Character Classes and Bracket Expressions.\n(line 62)\n* question mark: Fundamental Structure.\n(line 19)\n* quiet, silent: General Output Control.\n(line 78)\n* range expression: Character Classes and Bracket Expressions.\n(line 14)\n* recursive search: File and Directory Selection.\n(line 105)\n* recursive search <1>: File and Directory Selection.\n(line 113)\n* regular expressions: Regular Expressions. (line 6)\n* return status: Exit Status. (line 6)\n* rv GREPCOLORS capability: Environment Variables.\n(line 81)\n* searching directory trees: File and Directory Selection.\n(line 73)\n* searching directory trees <1>: File and Directory Selection.\n(line 83)\n* searching directory trees <2>: File and Directory Selection.\n(line 97)\n* searching directory trees <3>: File and Directory Selection.\n(line 105)\n* searching directory trees <4>: File and Directory Selection.\n(line 113)\n* searching for patterns: Introduction. (line 6)\n* sl GREPCOLORS capability: Environment Variables.\n(line 64)\n* space character class: Character Classes and Bracket Expressions.\n(line 67)\n* space characters: Character Classes and Bracket Expressions.\n(line 67)\n* special characters: Fundamental Structure.\n(line 6)\n* subexpression: Back-references and Subexpressions.\n(line 6)\n* suppress binary data: File and Directory Selection.\n(line 8)\n* suppress error messages: General Output Control.\n(line 85)\n* symbolic links: File and Directory Selection.\n(line 62)\n* symbolic links <1>: File and Directory Selection.\n(line 105)\n* symbolic links <2>: File and Directory Selection.\n(line 113)\n* tab-aligned content lines: Output Line Prefix Control.\n(line 41)\n* translation of message language: Environment Variables.\n(line 164)\n* upper character class: Character Classes and Bracket Expressions.\n(line 72)\n* upper-case letters: Character Classes and Bracket Expressions.\n(line 72)\n* usage summary, printing: Generic Program Information.\n(line 7)\n* usage, examples: Usage. (line 6)\n* using grep, Q&A: Usage. (line 32)\n* variants of grep: grep Programs. (line 6)\n* version, printing: Generic Program Information.\n(line 12)\n* whitespace characters: Character Classes and Bracket Expressions.\n(line 67)\n* with filename prefix: Output Line Prefix Control.\n(line 18)\n* xdigit character class: Character Classes and Bracket Expressions.\n(line 76)\n* xdigit class: Character Classes and Bracket Expressions.\n(line 76)\n* zero-terminated file names: Output Line Prefix Control.\n(line 50)\n* zero-terminated lines: Other Options. (line 43)\n\n", "subsections": [] } } } }