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📛 NAME

diff - compare files line by line

🚀 Quick Reference

Use Case	Command	Description
Compare two files	diff file1 file2	Show differences line by line (normal diff)
Unified diff with context	diff -u file1 file2	Compact format with 3 lines context
Side‑by‑side comparison	diff -y file1 file2	Two‑column output, easier to read
Recursive directory diff	diff -r dir1 dir2	Compare all files in subdirectories
Ignore whitespace	diff -w file1 file2	Skip all white‑space differences
Only report if files differ	diff -q file1 file2	Quiet mode, no detailed diff
Ignore case	diff -i file1 file2	Case‑insensitive comparison

📖 SYNOPSIS

diff [OPTION]... FILES

📝 DESCRIPTION

Compare FILES line by line.

Mandatory arguments to long options are mandatory for short options too.

• --normal 📋 output a normal diff (the default)
• -q, --brief 🏃 report only when files differ
• -s, --report-identical-files ✅ report when two files are the same
• -c, -C NUM, --context[=NUM] 📜 output NUM (default 3) lines of copied context
• -u, -U NUM, --unified[=NUM] 🔲 output NUM (default 3) lines of unified context
• -e, --ed 📝 output an ed script
• -n, --rcs 📦 output an RCS format diff
• -y, --side-by-side ↔️ output in two columns
• -W, --width=NUM 📏 output at most NUM (default 130) print columns
• --left-column ⬅️ output only the left column of common lines
• --suppress-common-lines 🙈 do not output common lines
• -p, --show-c-function 🧩 show which C function each change is in
• -F, --show-function-line=RE 🔍 show the most recent line matching RE
• --label LABEL 🏷️ use LABEL instead of file name and timestamp (can be repeated)
• -t, --expand-tabs ↹ expand tabs to spaces in output
• -T, --initial-tab ↔️ make tabs line up by prepending a tab
• --tabsize=NUM 📐 tab stops every NUM (default 8) print columns
• --suppress-blank-empty 🧹 suppress space or tab before empty output lines
• -l, --paginate 📄 pass output through 'pr' to paginate it
• -r, --recursive 🔁 recursively compare any subdirectories found
• --no-dereference 🔗 don't follow symbolic links
• -N, --new-file 🆕 treat absent files as empty
• --unidirectional-new-file ◀️ treat absent first files as empty
• --ignore-file-name-case 🔡 ignore case when comparing file names
• --no-ignore-file-name-case 🔤 consider case when comparing file names
• -x, --exclude=PAT 🚫 exclude files that match PAT
• -X, --exclude-from=FILE 📄🚫 exclude files that match any pattern in FILE
• -S, --starting-file=FILE 🏁 start with FILE when comparing directories
• --from-file=FILE1 📂 compare FILE1 to all operands; FILE1 can be a directory
• --to-file=FILE2 📂 compare all operands to FILE2; FILE2 can be a directory
• -i, --ignore-case 🔠 ignore case differences in file contents
• -E, --ignore-tab-expansion ↹ ignore changes due to tab expansion
• -Z, --ignore-trailing-space 🧼 ignore white space at line end
• -b, --ignore-space-change 🧽 ignore changes in the amount of white space
• -w, --ignore-all-space 🕊️ ignore all white space
• -B, --ignore-blank-lines 📭 ignore changes where lines are all blank
• -I, --ignore-matching-lines=RE 🎯 ignore changes where all lines match RE
• -a, --text 📄 treat all files as text
• --strip-trailing-cr 🔪 strip trailing carriage return on input
• -D, --ifdef=NAME 🛡️ output merged file with '#ifdef NAME' diffs
• --GTYPE-group-format=GFMT format GTYPE input groups with GFMT
• --line-format=LFMT format all input lines with LFMT
• --LTYPE-line-format=LFMT format LTYPE input lines with LFMT

These format options provide fine‑grained control over the output of diff, generalizing -D/--ifdef.

📐 Format Specifiers

LTYPE is 'old', 'new', or 'unchanged'. GTYPE is LTYPE or 'changed'.

GFMT (only) may contain:

• %< lines from FILE1
• %> lines from FILE2
• %= lines common to FILE1 and FILE2
• %[-][WIDTH][.[PREC]]{doxX}LETTER printf‑style spec for LETTER

LETTERs are as follows for new group, lower case for old group:

• F first line number
• L last line number
• N number of lines = L‑F+1
• E F‑1
• M L+1

%(A=B?T:E) if A equals B then T else E

LFMT (only) may contain:

• %L contents of line
• %l contents of line, excluding any trailing newline
• %[-][WIDTH][.[PREC]]{doxX}n printf‑style spec for input line number

Both GFMT and LFMT may contain:

• %% %
• %c'C' the single character C
• %c'\OOO' the character with octal code OOO
• C the character C (other characters represent themselves)

• -d, --minimal 🔬 try hard to find a smaller set of changes
• --horizon-lines=NUM 🌅 keep NUM lines of the common prefix and suffix
• --speed-large-files ⚡ assume large files and many scattered small changes
• --color[=WHEN] 🎨 color output; WHEN is 'never', 'always', or 'auto'; plain --color means --color='auto'
• --palette=PALETTE 🎨 the colors to use when --color is active; PALETTE is a colon‑separated list of terminfo capabilities
• --help ❓ display this help and exit
• -v, --version 🏷️ output version information and exit

FILES are 'FILE1 FILE2' or 'DIR1 DIR2' or 'DIR FILE' or 'FILE DIR'. If --from-file or --to-file is given, there are no restrictions on FILE(s). If a FILE is '-', read standard input. Exit status is 0 if inputs are the same, 1 if different, 2 if trouble.

🚪 Exit Codes

Code	Meaning
0	Inputs are identical
1	Inputs are different
2	Trouble (e.g., file not found, invalid option)

👤 AUTHOR

Written by Paul Eggert, Mike Haertel, David Hayes, Richard Stallman, and Len Tower.

🐛 REPORTING BUGS

Report bugs to: bug-diffutils AT gnu.org

GNU diffutils home page: <https://www.gnu.org/software/diffutils/>

General help using GNU software: <https://www.gnu.org/gethelp/>

©️ COPYRIGHT

Copyright © 2021 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>.

This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law.

📚 SEE ALSO

wdiff(1), cmp(1), diff3(1), sdiff(1), patch(1)

The full documentation for diff is maintained as a Texinfo manual. If the info and diff programs are properly installed at your site, the command

info diff

should give you access to the complete manual.

📛 NAME 🚀 Quick Reference 📖 SYNOPSIS 📝 DESCRIPTION 🚪 Exit Codes 👤 AUTHOR 🐛 REPORTING BUGS ©️ COPYRIGHT 📚 SEE ALSO