EXPAND(P) POSIX Programmer's Manual EXPAND(P)
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>s replaced with one or more <space>s needed to pad to the next tab stop. Any
<backspace>s 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
The expand utility shall conform to the Base Definitions volume of IEEE Std 1003.1-2001,
Section 12.2, Utility Syntax Guidelines.
The following option shall be supported:
Specify the tab stops. The application shall ensure that the argument tablist con-
sists of either a single positive decimal integer or a list of tabstops. If a sin-
gle 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>s or commas, in ascending
order. The tabs 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 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 IEEE Std 1003.1-2001, Section 8.2, Inter-
nationalization 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 interna-
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 argu-
ments and input files), the processing of <tab>s and <space>s, and for the determi-
nation of the width in column positions each character would occupy on an output
Determine the locale that should be used to affect the format and contents of diag-
nostic messages written to standard error.
Determine the location of message catalogs for the processing of LC_MESSAGES .
The standard output shall be equivalent to the input files with <tab>s converted into the
appropriate number of <space>s.
The standard error shall be used only for diagnostic messages.
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.
The expand utility is useful for preprocessing text files (before sorting, looking at spe-
cific columns, and so on) that contain <tab>s.
See the Base Definitions volume of IEEE Std 1003.1-2001, Section 3.103, Column Position.
The tablist option-argument consists of integers in ascending order. Utility Syntax Guide-
line 8 mandates that expand shall accept the integers (within the single argument) sepa-
rated using either commas or <blank>s.
tabs , unexpand
Portions of this text are reprinted and reproduced in electronic form from IEEE Std
1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System
Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 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 orig-
inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .
IEEE/The Open Group 2003 EXPAND(P)