expand(C)

expand -- convert tabs to spaces

Syntax

expand [ -t tablist ] [ file ... ]

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

unexpand [-a | -t tablist ] [ file ... ]

Description

expand reads either its standard input or the named files, replaces all tabs with spaces, and writes its output to the standard output. When a backspace character is encountered the column count is decremented (for tab stop calculations) and the backspace character is copied to the standard output unchanged.

The second form of expand uses a single number to specify the tab interval, tabstop, preceded by a minus sign. Multiple tab stops are specified after a leading minus sign as tab1, tab2 and so on.

unexpand reads the standard input or the named files, and replaces leading blanks with the maximum number of tabs followed by the minimum number of spaces necessary to provide an equivalent indentation. The output is then written to the standard output. If a backspace character is encountered in the input, unexpand decrements its column counter then copies the backspace character to the output.

By default, tab stops are set at every eighth column position.

The following options are recognized:

-a: By default, unexpand translates any leading blanks that it encounters. If the -a option is given, all sequences of two or more spaces preceding a tab stop are translated into the maximum corresponding number of tabs followed by the minimum number of spaces necessary to match the indentation.
-t tablist: tablist is a single argument consisting of positive integers separated by spaces or commas. If only a single number is given, tabs are set at column positions tablist columns apart, instead of the default. If multiple numbers are specified, tab stops are set at those column positions. No space to tab conversions are made by unexpand for positions past the last specified tab stop, and expand replaces any tabs past the last given tab stop with spaces (one space per tab).
When the -t option is used for unexpand, -a is assumed.

Exit values

expand and unexpand return the following values:

0: successful completion
>0: an error occurred

Examples

Convert tabs to spaces in tabbed.file, and send output to un.tabbed.file, where tabs are located at column positions in multiples of 5 spaces:

expand -t 5 <tabbed.file >un.tabbed.file

Convert spaces to tabs in txtfile, and send output to tabbed.file:

unexpand <txtfile >tabbed.file

Standards conformance

expand and unexpand are conformant with: