Software:head (Unix)
Example usage of head command to display first 5 lines of Lorem ipsum in the specified file | |
Developer(s) | Various open-source and commercial developers |
---|---|
Operating system | Unix, Unix-like, MSX-DOS, IBM i |
Platform | Cross-platform |
Type | Command |
License | coreutils: GPLv3 |
head is a program on Unix and Unix-like operating systems used to display the beginning of a text file or piped data.
Syntax
The command syntax is:
head [options] <file_name>
By default, head
will print the first 10 lines of its input to the standard output. The number of lines printed may be changed with a command line option. The following example shows the first 20 lines of filename:
head -n 20 filename
This displays the first 5 lines of all files starting with foo:
head -n 5 foo*
Most versions allow omitting n
and instead directly specifying the number: -5
. GNU head allows negative arguments for the -n
option, meaning to print all but the last - argument value counted - lines of each input file.
Flags
-c <x number of bytes> Copy first x number of bytes.
Other
Many early versions of Unix and Plan 9 did not have this command, and documentation and books used sed instead:
sed 5q filename
The example prints every line (implicit) and quit after the fifth.
Equivalently, awk may be used to print the first five lines in a file:
awk 'NR < 6' filename
However, neither sed nor awk were available in early versions of BSD, which were based on Version 6 Unix, and included head.[1]
Implementations
A head
command is also part of ASCII's MSX-DOS2 Tools for MSX-DOS version 2.[2] The head command has also been ported to the IBM i operating system.[3]
See also
References
- ↑ Spinellis, Diomidis (2022). "dspinellis/unix-history-man: Version 1.0 web pages (v1.1-web)". Zenodo. doi:10.5281/zenodo.7248228. https://dspinellis.github.io/unix-history-man/man1.html.
- ↑ MSX-DOS2 Tools User's Manual by ASCII Corporation
- ↑ IBM. "IBM System i Version 7.2 Programming Qshell" (in en). https://www.ibm.com/support/knowledgecenter/ssw_ibm_i_74/rzahz/rzahzpdf.pdf?view=kc.
External links
- head manual page from GNU coreutils.
- FreeBSD documentation for head
Original source: https://en.wikipedia.org/wiki/Head (Unix).
Read more |