Английская Википедия:Head (Unix)

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Шаблон:More citations needed Шаблон:Short description Шаблон:Lowercase Шаблон:Infobox software 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 versionsШаблон:Citation needed 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.

Implementations

A head command is also part of ASCII's MSX-DOS2 Tools for MSX-DOS version 2. The Шаблон:Mono command has also been ported to the IBM i operating system.

See also

• tail (Unix)
• dd (Unix)
• List of Unix commands

External links

• head manual page from GNU coreutils.
• FreeBSD documentation for head