PROLOG

       This  manual  page  is part of the POSIX Programmer's Manual.  The Linux implementation of
       this interface may differ (consult the corresponding Linux  manual  page  for  details  of
       Linux behavior), or the interface may not be implemented on Linux.

NAME

       expand — convert tabs to spaces

SYNOPSIS

       expand [−t tablist] [file...]

DESCRIPTION

       The  expand  utility  shall  write files or the standard input to the standard output with
       <tab> characters replaced with one or more <space> characters needed to pad  to  the  next
       tab  stop.  Any  <backspace> characters shall be copied to the output and cause the column
       position count for tab stop calculations to be  decremented;  the  column  position  count
       shall not be decremented below zero.

OPTIONS

       The  expand  utility shall conform to the Base Definitions volume of POSIX.1‐2008, Section
       12.2, Utility Syntax Guidelines.

       The following option shall be supported:

       −t tablist
                 Specify the tab stops. The application shall ensure that  the  argument  tablist
                 consists of either a single positive decimal integer or a list of tabstops. If a
                 single number is given, tabs shall be set that number of column positions  apart
                 instead of the default 8.

                 If a list of tabstops is given, the application shall ensure that it consists of
                 a list of two or more positive decimal integers, separated by <blank> or <comma>
                 characters,  in  ascending  order.  The  <tab>  characters shall be set at those
                 specific column positions. Each tab stop N shall be  an  integer  value  greater
                 than  zero,  and  the list is 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.

                 In  the  event of expand having to process a <tab> at a position beyond the last
                 of those specified in a multiple tab-stop list, the <tab> shall be replaced by a
                 single <space> in the output.

OPERANDS

       The following operand shall be supported:

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

STDIN

       See the INPUT FILES section.

INPUT FILES

       Input files shall be text files.

ENVIRONMENT VARIABLES

       The following environment variables shall affect the execution of expand:

       LANG      Provide a default value for the internationalization variables that are unset or
                 null.  (See  the  Base  Definitions  volume  of   POSIX.1‐2008,   Section   8.2,
                 Internationalization   Variables  for  the  precedence  of  internationalization
                 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  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 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 <tab> characters converted
       into the appropriate number of <space> characters.

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

       The  expand  utility  shall  terminate with an error message and non-zero exit status upon
       encountering difficulties accessing one of the file operands.

       The following sections are informative.

APPLICATION USAGE

       None.

EXAMPLES

       None.

RATIONALE

       The expand utility is useful for preprocessing text  files  (before  sorting,  looking  at
       specific columns, and so on) that contain <tab> characters.

       See the Base Definitions volume of POSIX.1‐2008, Section 3.103, Column Position.

       The  tablist  option-argument  consists  of  integers  in  ascending order. Utility Syntax
       Guideline 8 mandates that expand shall accept the integers (within  the  single  argument)
       separated using either <comma> or <blank> characters.

       Earlier versions of this standard allowed the following form in the SYNOPSIS:

           expand [−tabstop][−tab1,tab2,...,tabn][file ...]

       This   form   is  no  longer  specified  by  POSIX.1‐2008  but  may  be  present  in  some
       implementations.

FUTURE DIRECTIONS

       None.

SEE ALSO

       tabs, unexpand

       The Base Definitions volume of POSIX.1‐2008, Section 3.103, Column  Position,  Chapter  8,
       Environment Variables, Section 12.2, Utility Syntax Guidelines

COPYRIGHT

       Portions  of  this  text  are  reprinted  and  reproduced in electronic form from IEEE Std
       1003.1, 2013 Edition, Standard for Information Technology  --  Portable  Operating  System
       Interface  (POSIX),  The Open Group Base Specifications Issue 7, Copyright (C) 2013 by the
       Institute of Electrical and Electronics Engineers, Inc  and  The  Open  Group.   (This  is
       POSIX.1-2008  with  the  2013  Technical  Corrigendum  1  applied.)  In  the  event of any
       discrepancy between this version and the original IEEE and The Open  Group  Standard,  the
       original  IEEE  and The Open Group Standard is the referee document. The original Standard
       can be obtained online at http://www.unix.org/online.html .

       Any typographical or formatting errors that appear in this page are most  likely  to  have
       been  introduced  during  the conversion of the source files to man page format. To report
       such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .