freebsd/bin/cat/cat.1

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.\"     @(#)cat.1	8.3 (Berkeley) 5/2/95
.\" $FreeBSD$
.\"
.Dd January 29, 2013
.Dt CAT 1
.Os
.Sh NAME
.Nm cat
.Nd concatenate and print files
.Sh SYNOPSIS
.Nm
.Op Fl belnstuv
.Op Ar
.Sh DESCRIPTION
The
.Nm
utility reads files sequentially, writing them to the standard output.
The
.Ar file
operands are processed in command-line order.
If
.Ar file
is a single dash
.Pq Sq Fl
or absent,
.Nm
reads from the standard input.
If
.Ar file
is a
.Ux
domain socket,
.Nm
connects to it and then reads it until
.Dv EOF .
This complements the
.Ux
domain binding capability available in
.Xr inetd 8 .
.Pp
The options are as follows:
.Bl -tag -width indent
.It Fl b
Number the non-blank output lines, starting at 1.
.It Fl e
Display non-printing characters (see the
.Fl v
option), and display a dollar sign
.Pq Ql \&$
at the end of each line.
.It Fl l
Set an exclusive advisory lock on the standard output file descriptor.
This lock is set using
.Xr fcntl 2
with the
.Dv F_SETLKW
command.
If the output file is already locked,
.Nm
will block until the lock is acquired.
.It Fl n
Number the output lines, starting at 1.
.It Fl s
Squeeze multiple adjacent empty lines, causing the output to be
single spaced.
.It Fl t
Display non-printing characters (see the
.Fl v
option), and display tab characters as
.Ql ^I .
.It Fl u
Disable output buffering.
.It Fl v
Display non-printing characters so they are visible.
Control characters print as
.Ql ^X
for control-X; the delete
character (octal 0177) prints as
.Ql ^? .
.Pf Non- Tn ASCII
characters (with the high bit set) are printed as
.Ql M-
(for meta) followed by the character for the low 7 bits.
.El
.Sh EXIT STATUS
.Ex -std
.Sh EXAMPLES
The command:
.Pp
.Dl "cat file1"
.Pp
will print the contents of
.Pa file1
to the standard output.
.Pp
The command:
.Pp
.Dl "cat file1 file2 > file3"
.Pp
will sequentially print the contents of
.Pa file1
and
.Pa file2
to the file
.Pa file3 ,
truncating
.Pa file3
if it already exists.
See the manual page for your shell (e.g.,
.Xr sh 1 )
for more information on redirection.
.Pp
The command:
.Pp
.Dl "cat file1 - file2 - file3"
.Pp
will print the contents of
.Pa file1 ,
print data it receives from the standard input until it receives an
.Dv EOF
.Pq Sq ^D
character, print the contents of
.Pa file2 ,
read and output contents of the standard input again, then finally output
the contents of
.Pa file3 .
Note that if the standard input referred to a file, the second dash
on the command-line would have no effect, since the entire contents of the file
would have already been read and printed by
.Nm
when it encountered the first
.Sq Fl
operand.
.Sh SEE ALSO
.Xr head 1 ,
.Xr more 1 ,
.Xr pr 1 ,
.Xr sh 1 ,
.Xr tail 1 ,
.Xr vis 1 ,
.Xr zcat 1 ,
.Xr fcntl 2 ,
.Xr setbuf 3
.Rs
.%A Rob Pike
.%T "UNIX Style, or cat -v Considered Harmful"
.%J "USENIX Summer Conference Proceedings"
.%D 1983
.Re
.Sh STANDARDS
The
.Nm
utility is compliant with the
.St -p1003.2-92
specification.
.Pp
The flags
.Op Fl belnstv
are extensions to the specification.
.Sh HISTORY
A
.Nm
utility appeared in
.At v1 .
.An Dennis Ritchie
designed and wrote the first man page.
It appears to have been
.Xr cat 1 .
.Sh BUGS
Because of the shell language mechanism used to perform output
redirection, the command
.Dq Li cat file1 file2 > file1
will cause the original data in
.Pa file1
to be destroyed!
.Pp
The
.Nm
utility does not recognize multibyte characters when the
.Fl t
or
.Fl v
option is in effect.