unexpand(1)

NAME
     unexpand - convert spaces to tabs

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

DESCRIPTION
     The unexpand utility copies files or the standard input to the standard
     output, converting blank characters at the beginning of each line into
     the maximum number of tab characters followed by the minimum number of
     space characters needed to fill the same column positions originally
     filled by the translated blank characters. By default, tabstops are set
     at every eighth column position. Each backspace character is copied to
     the output, and causes the column position count for tab calculations to
     be decremented; the count will never be decremented to a value less than
     one.

OPTIONS
     The following options are supported:

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

     -t tablist
          Specify the tab stops. The option-argument tablist must be a single
          argument consisting  of a single positive decimal integer or
          multiple positive decimal integers, separated by blank characters or
          commas, in ascending order. If a single number is given, tabs will
          be set tablist column positions apart instead of the default 8.  If
          multiple numbers are given, the tabs will be set at those specific
          column positions.

          Each tab-stop position N must be an integer value greater than zero,
          and the list must be in strictly ascending order. This is taken to
          mean that, from the start of a line of output, tabbing to position N
          causes 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 is the equivalent of specifying -t 8 (except for the
          interaction with -a, described below).

          No space-to-tab character conversions 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 is
          ignored; conversion will not be limited to the processing of leading
          blank characters.
OPERANDS
     The following operand is supported:

     -t file   The pathname of a text file to be used as input.

STDIN
     See INPUT FILES.

INPUT FILES
     Input files must be text files.

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

     LANG      Provide a default value for the internationalisation variables
     that are unset or null. If LANG is unset or null, the corresponding value
     from the implementation-specific default locale will be used. If any of
     the internationalisation variables contains an invalid setting, the
     utility will behave as if none of the variables had been defined.

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

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

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


ASYNCHRONOUS EVENTS
     Default.


STDOUT
     The standard output is equivalent to the input files with the specified
     space to tab character conversions.


STDERR
     Used only for diagnostic messages.


OUTPUT FILES
     None.

EXTENDED DESCRIPTION
     None.


EXIT STATUS
     The following exit values are returned:

     0 Successful completion.

     >0 An error occurred.


CONSEQUENCES OF ERRORS
     Default.


APPLICATION USAGE
     One non-intuitive aspect of unexpand is its restriction to leading spaces
     when neither -a nor -t is specified. Users who desire to always convert
     all spaces in a file can easily alias unexpand to use the -a or -t 8
     option.


EXAMPLES
     None.


FUTURE DIRECTIONS
     None.


SEE ALSO
     tabs, expand


CHANGE HISTORY
     First released in Issue 4.