Gnu/coreutils/head-invocation

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5.1 head: Output the first part of files

head prints the first part (10 lines by default) of each file; it reads from standard input if no files are given or when given a file of -. Synopsis:

head [option]… [file]…

If more than one file is specified, head prints a one-line header consisting of:

==> file name <==

before the output for each file.

The program accepts the following options. Also see Common options.

‘-c [-]num’
‘--bytes=[-]num’

Print the first num bytes, instead of initial lines. However, if num is prefixed with a ‘-’, print all but the last num bytes of each file. num may be, or may be an integer optionally followed by, one of the following multiplicative suffixes:

‘b’  =>            512 ("blocks")
‘KB’ =>           1000 (KiloBytes)
‘K’  =>           1024 (KibiBytes)
‘MB’ =>      1000*1000 (MegaBytes)
‘M’  =>      1024*1024 (MebiBytes)
‘GB’ => 1000*1000*1000 (GigaBytes)
‘G’  => 1024*1024*1024 (GibiBytes)

and so on for ‘T’, ‘P’, ‘E’, ‘Z’, and ‘Y’. Binary prefixes can be used, too: ‘KiB’=‘K’, ‘MiB’=‘M’, and so on.

‘-n [-]num’
‘--lines=[-]num’

Output the first num lines. However, if num is prefixed with a ‘-’, print all but the last num lines of each file. Size multiplier suffixes are the same as with the -c option.

‘-q’
‘--quiet’
‘--silent’

Never print file name headers.

‘-v’
‘--verbose’

Always print file name headers.

‘-z’
‘--zero-terminated’

Delimit items with a zero byte rather than a newline (ASCII LF). I.e., treat input as items separated by ASCII NUL and terminate output items with ASCII NUL. This option can be useful in conjunction with ‘perl -0’ or ‘find -print0’ and ‘xargs -0’ which do the same in order to reliably handle arbitrary file names (even those containing blanks or other special characters).

For compatibility head also supports an obsolete option syntax -[num][bkm][cqv], which is recognized only if it is specified first. num is a decimal number optionally followed by a size letter (‘b’, ‘k’, ‘m’) as in -c, or ‘l’ to mean count by lines, or other option letters (‘cqv’). Scripts intended for standard hosts should use -c num or -n num instead. If your script must also run on hosts that support only the obsolete syntax, it is usually simpler to avoid head, e.g., by using ‘sed 5q’ instead of ‘head -5’.

An exit status of zero indicates success, and a nonzero value indicates failure.

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