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PROLOG
This manual page is part of the POSIX Programmer's Manual. The Linux implementation of
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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.1‐2017, 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.1‐2017, 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.1‐2017, 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.1‐2017, 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
1003.1-2017, Standard for Information Technology -- Portable Operating System Interface
(POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by
the Institute of Electrical and Electronics Engineers, Inc and The Open Group. 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.opengroup.org/unix/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 .