Expand (Unix)
Encyclopedia
expand is a program that converts tab character
s into groups of space
characters. It is available in Unix
operating system
s and many Unix-like
operating systems.
For example:
$ echo -e "foo\tbar" | expand | xxd -g 1 -u
0000000: 66 6F 6F 20 20 20 20 20 62 61 72 0A foo bar.
$ echo -e "foo\tbar" | xxd -g 1 -u
0000000: 66 6F 6F 09 62 61 72 0A foo.bar.
$
Here the echo command prints a string of text that includes a tab character, then the output is directed into the expand command. The resulting output is then displayed in hexadecimal
and as characters by the xxd dump command. At the second prompt, the same echo output is sent directly to the xxd command. As can be seen by comparing the two, the expand program converts the tab (specified as '\t' to the echo program) into spaces.
Character (computing)
In computer and machine-based telecommunications terminology, a character is a unit of information that roughly corresponds to a grapheme, grapheme-like unit, or symbol, such as in an alphabet or syllabary in the written form of a natural language....
s into groups of space
Space (punctuation)
In writing, a space is a blank area devoid of content, serving to separate words, letters, numbers, and punctuation. Conventions for interword and intersentence spaces vary among languages, and in some cases the spacing rules are quite complex....
characters. It is available in Unix
Unix
Unix is a multitasking, multi-user computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna...
operating system
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...
s and many Unix-like
Unix-like
A Unix-like operating system is one that behaves in a manner similar to a Unix system, while not necessarily conforming to or being certified to any version of the Single UNIX Specification....
operating systems.
For example:
$ echo -e "foo\tbar" | expand | xxd -g 1 -u
0000000: 66 6F 6F 20 20 20 20 20 62 61 72 0A foo bar.
$ echo -e "foo\tbar" | xxd -g 1 -u
0000000: 66 6F 6F 09 62 61 72 0A foo.bar.
$
Here the echo command prints a string of text that includes a tab character, then the output is directed into the expand command. The resulting output is then displayed in hexadecimal
Hexadecimal
In mathematics and computer science, hexadecimal is a positional numeral system with a radix, or base, of 16. It uses sixteen distinct symbols, most often the symbols 0–9 to represent values zero to nine, and A, B, C, D, E, F to represent values ten to fifteen...
and as characters by the xxd dump command. At the second prompt, the same echo output is sent directly to the xxd command. As can be seen by comparing the two, the expand program converts the tab (specified as '\t' to the echo program) into spaces.