unexpand(1p) - phpMan

UNEXPAND(P) UNEXPAND(P)

NAME
unexpand - convert spaces to tabs

SYNOPSIS
unexpand [ -a| -t tablist][file...]

DESCRIPTION
The unexpand utility shall copy files or standard input to standard output, con-
verting <blank>s at the beginning of each line into the maximum number of <tab>s
followed by the minimum number of <space>s needed to fill the same column positions
originally filled by the translated <blank>s. By default, tabstops shall be set at
every eighth column position. Each <backspace> shall be copied to the output, and
shall cause the column position count for tab calculations to be decremented; the
count shall never be decremented to a value less than one.

OPTIONS
The unexpand utility shall conform to the Base Definitions volume of
IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guidelines.

The following options shall be supported:

-a In addition to translating <blank>s at the beginning of each line, translate
all sequences of two or more <blank>s immediately preceding a tab stop to
the maximum number of <tab>s followed by the minimum number of <space>s
needed to fill the same column positions originally filled by the translated
<blank>s.

-t tablist
Specify the tab stops. The application shall ensure that the tablist option-
argument is a single argument consisting of a single positive decimal inte-
ger or multiple positive decimal integers, separated by <blank>s or commas,
in ascending order. If a single number is given, tabs shall be set tablist
column positions apart instead of the default 8. If multiple numbers are
given, the tabs shall be set at those specific column positions.

The application shall ensure that each tab-stop position N is an integer value
greater than zero, and the list shall be in strictly ascending order. This is taken
to mean that, from the start of a line of output, tabbing to position N shall cause
the next character output to be in the ( N+1)th column position on that line. When
the -t option is not specified, the default shall be the equivalent of specifying
-t 8 (except for the interaction with -a, described below).

No <space>-to- <tab> conversions shall occur for characters at positions beyond the
last of those specified in a multiple tab-stop list.

When -t is specified, the presence or absence of the -a option shall be ignored;
conversion shall not be limited to the processing of leading <blank>s.

OPERANDS
The following operand shall be supported:

file A pathname of a text file to be used as input.

STDIN
See the INPUT FILES section.

INPUT FILES
The input files shall be text files.

ENVIRONMENT VARIABLES
The following environment variables shall affect the execution of unexpand:

LANG Provide a default value for the internationalization variables that are
unset or null. (See the Base Definitions volume of IEEE Std 1003.1-2001,
Section 8.2, Internationalization Variables for the precedence of interna-
tionalization variables used to determine the values of locale categories.)

LC_ALL If set to a non-empty string value, override the values of all the other
internationalization variables.

LC_CTYPE
Determine the locale for the interpretation of sequences of bytes of text
data as characters (for example, single-byte as opposed to multi-byte char-
acters in arguments and input files), the processing of <tab>s and <space>s,
and for the determination of the width in column positions each character
would occupy on an output device.

LC_MESSAGES
Determine the locale that should be used to affect the format and contents
of diagnostic messages written to standard error.

NLSPATH
Determine the location of message catalogs for the processing of LC_MESSAGES
.

ASYNCHRONOUS EVENTS
Default.

STDOUT
The standard output shall be equivalent to the input files with the specified
<space>-to- <tab> conversions.

STDERR
The standard error shall be used only for diagnostic messages.

OUTPUT FILES
None.

EXTENDED DESCRIPTION
None.

EXIT STATUS
The following exit values shall be returned:

0 Successful completion.

>0 An error occurred.

CONSEQUENCES OF ERRORS
Default.

The following sections are informative.

APPLICATION USAGE
One non-intuitive aspect of unexpand is its restriction to leading spaces when nei-
ther -a nor -t is specified. Users who always want to convert all spaces in a file
can easily alias unexpand to use the -a or -t 8 option.

EXAMPLES
None.

RATIONALE
On several occasions, consideration was given to adding a -t option to the unexpand
utility to complement the -t in expand (see expand ). The historical intent of
unexpand was to translate multiple <blank>s into tab stops, where tab stops were a
multiple of eight column positions on most UNIX systems. An early proposal omitted
-t because it seemed outside the scope of the User Portability Utilities option; it
was not described in any of the base documents. However, hard-coding tab stops
every eight columns was not suitable for the international community and broke his-
torical precedents for some vendors in the FORTRAN community, so -t was restored in
conjunction with the list of valid extension categories considered by the standard
developers. Thus, unexpand is now the logical converse of expand.

FUTURE DIRECTIONS
None.