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man pages section 1: User Commands

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Updated: Thursday, March 14, 2019
 
 

unexpand(1)

Name

expand, unexpand - expand TAB characters to SPACE characters, and vice versa

Synopsis

expand [-i | --initial] [
--help] [-t | --tabs 
tablist] [file]... 
expand [-i | --initial] [
--help] [-tabstop] 
            [tab1, tab2,. .    ., 
tabn] [file]...

Description

The expand utility copies files (or the standard input) to the standard output, with TAB characters expanded to SPACE characters. BACKSPACE characters are preserved into the output and decrement the column count for TAB calculations. expand is useful for pre-processing character files (before sorting, looking at specific columns, and so forth) that contain TAB characters.

unexpand copies files (or the standard input) to the standard output, putting TAB characters back into the data. By default, only leading SPACE and TAB characters are converted to strings of tabs, but this can be overridden by the –a option (see the OPTIONS section below).

Options

The following options are supported for expand:

–t, –-tabs tablist

Specifies the tab stops. The argument tablist must consist 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.

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

–i, –-initial

Do not convert any TABs after non-SPACE characters are encountered.

tabstop

Specifies as a single argument, sets TAB characters tabstop SPACE characters apart instead of the default 8.

tab1 , tab2,...,tabn

Sets TAB characters at the columns specified by tab1,tab2,..., tabn

–-help

Print command usage and exit.

The following options are supported for unexpand:

–a, –-all

Inserts TAB characters when replacing a run of two or more SPACE characters would produce a smaller output file.

–-first-only

Converts only leading sequences of SPACEs. This option overrides – a.

–t, –-tabs tablist

Specifies 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 will cause 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 for expand and unexpand:

file

The path name of a text file to be used as input.

Environment Variables

See environ(7) for descriptions of the following environment variables that affect the execution of expand and unexpand: LANG, LC_ALL, LC_CTYPE, LC_MESSAGES, and NLSPATH.

Exit Status

The following exit values are returned:

0

Successful completion

>0

An error occurred.

Attributes

See attributes(7) for descriptions of the following attributes:

ATTRIBUTE TYPE
ATTRIBUTE VALUE
Availability
system/core-os
CSI
enabled
Interface Stability
Committed
Standard

See Also

tabs(1), attributes(7), environ(7), standards(7)