path: root/usr/src/man/man1/head.1

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.TH HEAD 1 "Mar 4, 2013"
.SH NAME
head \- display first few lines of files
.SH SYNOPSIS
.SS "/usr/bin/head"
.LP
.nf
\fB/usr/bin/head\fR [\fB-q\fR] [\fB-v\fR] [\fB-number\fR ] [ \fB-n\fR \fInumber\fR ] [ \fB-c\fR \fInumber\fR] [\fIfilename\fR]...
.fi

.SS "ksh93"
.LP
.nf
\fBhead\fR [\fB-qv\fR] [\fB-n\fR \fIlines\fR] [\fB-c\fR \fIchars\fR] [\fB-s\fR \fIskip\fR] [\fIfilename\fR]...
.fi

.SH DESCRIPTION
.SS "/usr/bin/head"
.sp
.LP
The \fBhead\fR utility copies the first \fInumber\fR of lines of each
\fIfilename\fR to the standard output. If no \fIfilename\fR is given,
\fBhead\fR copies lines from the standard input. The default value of
\fInumber\fR is \fB10\fR lines. If \fB-c\fR is specified, \fBhead\fR
copies the first \fInumber\fR of bytes of each filename.
.sp
.LP
When more than one file is specified, the start of each file looks like:
.sp
.in +2
.nf
\fB==>\fR \fIfilename\fR \fB<==\fR
.fi
.in -2

.sp
.LP
Thus, a common way to display a set of short files, identifying each one, is:
.sp
.in +2
.nf
example% \fBhead -9999 filename1 filename2 ...\fR
.fi
.in -2
.sp

.SS "ksh93"
.sp
.LP
The \fBhead\fR built-in in \fBksh93\fR is associated with the \fB/bin\fR and
\fB/usr/bin\fR paths. It is invoked when \fBhead\fR is executed without a
pathname prefix and the pathname search finds a \fB/bin/head\fR or
\fB/usr/bin/head\fR executable.
.sp
.LP
\fBhead\fR copies one or more input files to standard output, stopping at a
designated point for each file or to the end of the file whichever comes first.
Copying ends at the point indicated by the options. By default, a header of the
form \fB==> filename <==\fR is output before all but the first file but this
can be changed with the \fB-q\fR and \fB-v\fR options. If no file is given, or
if the file is \fB-\fR, \fBhead\fR copies from standard input starting at the
current location.
.sp
.LP
The option argument for \fB-c\fR and \fB-s\fR can optionally be followed by one
of the following characters to specify a different unit other than a single
byte:
.sp
.ne 2
.na
\fB\fBb\fR\fR
.ad
.RS 5n
512 bytes
.RE

.sp
.ne 2
.na
\fB\fBk\fR\fR
.ad
.RS 5n
1-kilobyte
.RE

.sp
.ne 2
.na
\fB\fBm\fR\fR
.ad
.RS 5n
1-megabyte
.RE

.sp
.LP
For backwards compatibility, \fB-number\fR is equivalent to \fB-n\fR number.
.SH OPTIONS
.SS "/usr/bin/head"
.sp
.LP
The following options are supported by \fB/usr/bin/head\fR:
.sp
.ne 2
.na
\fB\fB-n\fR \fInumber\fR\fR
.ad
.RS 13n
The first \fInumber\fR lines of each input file is copied to standard output.
The \fInumber\fR option-argument must be a positive decimal integer.
.RE

.sp
.ne 2
.na
\fB\fB-c\fR \fInumber\fR\fR
.ad
.RS 13n
The first \fInumber\fR bytes of each input file is copied to standard output.
The \fInumber\fR option-argument must be a positive decimal integer. Note,
output may end in the middle of a character if a file contains multi-byte
characters.
.RE

.sp
.ne 2
.na
\fB\fB-\fR\fInumber\fR\fR
.ad
.RS 13n
The \fInumber\fR argument is a positive decimal integer with the same effect as
the \fB-n\fR \fInumber\fR option.
.RE

.sp
.ne 2
.na
\fB-q\fR
.ad
.RS 13n
\fBhead\fR will not print a header in between each specified file.
.RE

.sp
.ne 2
.na
\fB-v\fR
.ad
.RS 13n
\fBhead\fR will always print a header in between each specified file.
.RE

.sp
.LP
If no options are specified, \fBhead\fR acts as if \fB-n\fR \fB10\fR had been
specified.
.SS "ksh93"
.sp
.LP
The following options are supported by the head built-in command in
\fBksh93\fR:
.sp
.ne 2
.na
\fB\fB-n\fR\fR
.ad
.br
.na
\fB\fB--lines=\fR\fIlines\fR\fR
.ad
.RS 18n
Copy lines from each file. The default value is \fB10\fR.
.RE

.sp
.ne 2
.na
\fB\fB-c\fR\fR
.ad
.br
.na
\fB\fB--bytes=\fR\fIchars\fR\fR
.ad
.RS 18n
Copy \fIchars\fR bytes from each file.
.RE

.sp
.ne 2
.na
\fB\fB-q\fR\fR
.ad
.br
.na
\fB\fB--quiet|silent\fR\fR
.ad
.RS 18n
Never output filename headers.
.RE

.sp
.ne 2
.na
\fB\fB-s\fR\fR
.ad
.br
.na
\fB\fB--skip=\fR\fIskip\fR\fR
.ad
.RS 18n
Skip \fIskip\fR characters or lines from each file before copying.
.RE

.sp
.ne 2
.na
\fB\fB-v\fR\fR
.ad
.br
.na
\fB\fB--verbose\fR\fR
.ad
.RS 18n
Always output filename headers.
.RE

.SH OPERANDS
.sp
.LP
The following operand is supported:
.sp
.ne 2
.na
\fB\fB\fIfilename\fR\fR\fR
.ad
.RS 12n
A path name of an input file. If no \fIfile\fR operands are specified, the
standard input is used.
.RE

.SH USAGE
.sp
.LP
See \fBlargefile\fR(5) for the description of the behavior of \fBhead\fR when
encountering files greater than or equal to 2 Gbyte ( 2^31 bytes).
.SH EXAMPLES
.LP
\fBExample 1 \fRWriting the First Ten Lines of All Files
.sp
.LP
The following example writes the first ten lines of all files, except those
with a leading period, in the directory:

.sp
.in +2
.nf
example% \fBhead *\fR
.fi
.in -2
.sp

.SH ENVIRONMENT VARIABLES
.sp
.LP
See \fBenviron\fR(5) for descriptions of the following environment variables
that affect the execution of \fBhead\fR: \fBLANG\fR, \fBLC_ALL\fR,
\fBLC_CTYPE\fR, \fBLC_MESSAGES\fR, and \fBNLSPATH\fR.
.SH EXIT STATUS
.sp
.LP
The following exit values are returned:
.sp
.ne 2
.na
\fB\fB0\fR\fR
.ad
.RS 6n
Successful completion.
.RE

.sp
.ne 2
.na
\fB\fB>0\fR\fR
.ad
.RS 6n
An error occurred.
.RE

.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(5) for descriptions of the following attributes:
.SS "/usr/bin/head"
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
CSI	Enabled
_
Interface Stability	Committed
_
Standard	See \fBstandards\fR(5).
.TE

.SS "ksh93"
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	See below.
.TE

.sp
.LP
The \fBksh93\fR built-in binding to \fB/bin\fR and \fB/usr/bin\fR is Volatile.
The built-in interfaces are Uncommitted.
.SH SEE ALSO
.sp
.LP
\fBcat\fR(1), \fBksh93\fR(1), \fBmore\fR(1), \fBpg\fR(1), \fBtail\fR(1),
\fBattributes\fR(5), \fBenviron\fR(5), \fBlargefile\fR(5), \fBstandards\fR(5)