path: root/bin/cat/cat.1

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.\"     @(#)cat.1	8.3 (Berkeley) 5/2/95
.\"
.Dd June 15, 2014
.Dt CAT 1
.Os
.Sh NAME
.Nm cat
.Nd concatenate and print files
.Sh SYNOPSIS
.Nm
.Op Fl beflnstuv
.Op Fl B Ar bsize
.Op Fl
.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.
A single dash represents the standard input,
and may appear multiple times in the
.Ar file
list.
If no
.Ar file
operands are given, standard input is read.
.Pp
The word
.Dq concatenate
is just a verbose synonym for
.Dq catenate .
.Pp
The options are as follows:
.Bl -tag -width Ds
.It Fl B Ar bsize
Read with a buffer size of
.Ar bsize
bytes, instead of the default buffer size which is the blocksize of the
output file.
.It Fl b
Implies the
.Fl n
option, but doesn't number blank lines.
.It Fl e
Implies the
.Fl v
option, and displays a dollar sign
.Pq Ql \&$
at the end of each line
as well.
.It Fl f
Only attempt to display regular files.
.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
Implies the
.Fl v
option, and displays tab characters as
.Ql ^I
as well.
.It Fl u
The
.Fl u
option guarantees that the output is unbuffered.
.It Fl v
Displays non-printing characters so they are visible.
Control characters print as
.Ql ^X
for control-X; the delete
character (octal 0177) prints as
.Ql ^? .
Non-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 cat
.Sh EXAMPLES
The command:
.Bd -literal -offset indent
.Ic cat file1
.Ed
.Pp
will print the contents of
.Ar file1
to the standard output.
.Pp
The command:
.Bd -literal -offset indent
.Ic cat file1 file2 > file3
.Ed
.Pp
will sequentially print the contents of
.Ar file1
and
.Ar file2
to the file
.Ar file3 ,
truncating
.Ar 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:
.Bd -literal -offset indent
.Ic cat file1 - file2 - file3
.Ed
.Pp
will print the contents of
.Ar file1 ,
print data it receives from the standard input until it receives an
.Dv EOF
.Pq Sq ^D
character, print the contents of
.Ar file2 ,
read and output contents of the standard input again, then finally output
the contents of
.Ar 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
.Ql \&-
operand.
.Sh SEE ALSO
.Xr head 1 ,
.Xr hexdump 1 ,
.Xr lpr 1 ,
.Xr more 1 ,
.Xr pr 1 ,
.Xr tac 1 ,
.Xr tail 1 ,
.Xr view 1 ,
.Xr vis 1 ,
.Xr fcntl 2
.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 expected to conform to the
.St -p1003.2-92
specification.
.Pp
The flags
.Op Fl Bbeflnstv
are extensions to the specification.
.Sh HISTORY
A
.Nm
utility appeared in
.At v1 .
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 file1 to be destroyed!
This is performed by the shell before
.Nm
is run.