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, ifnum
is prefixed with a ‘-
’, print all but the lastnum
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, ifnum
is prefixed with a ‘-
’, print all but the lastnum
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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