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PROLOG | NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OPERANDS | STDIN | INPUT FILES | ENVIRONMENT VARIABLES | ASYNCHRONOUS EVENTS | STDOUT | STDERR | OUTPUT FILES | EXTENDED DESCRIPTION | EXIT STATUS | CONSEQUENCES OF ERRORS | APPLICATION USAGE | EXAMPLES | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
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EXPAND(1P) POSIX Programmer's Manual EXPAND(1P)
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.
expand — convert tabs to spaces
expand [-t tablist] [file...]
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.
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.
The following operand shall be supported:
file The pathname of a text file to be used as input.
See the INPUT FILES section.
Input files shall be text files.
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.
Default.
The standard output shall be equivalent to the input files with
<tab> characters converted into the appropriate number of <space>
characters.
The standard error shall be used only for diagnostic messages.
None.
None.
The following exit values shall be returned:
0 Successful completion
>0 An error occurred.
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.
None.
None.
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.
None.
tabs(1p), unexpand(1p)
The Base Definitions volume of POSIX.1‐2017, Section 3.103, Column
Position, Chapter 8, Environment Variables, Section 12.2, Utility
Syntax Guidelines
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 .
IEEE/The Open Group 2017 EXPAND(1P)
Pages that refer to this page: pr(1p), tabs(1p), unexpand(1p)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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