NAME
cat
- concatenate and print files
SYNOPSIS
cat
[-beflnstuv]
[-]
[]
DESCRIPTION
The
cat
utility reads files sequentially, writing them to the standard output.
The
file
operands are processed in command line order.
A single dash represents the standard input,
and may appear multiple times in the
file
list.
The word
``concatenate''
is just a verbose synonym for
``catenate''.
The options are as follows:
- -b
-
Implies the
-n
option but doesn't number blank lines.
- -e
-
Implies the
-v
option, and displays a dollar sign
(`$')
at the end of each line
as well.
- -f
-
Only attempt to display regular files.
- -l
-
Set an exclusive advisory lock on the standard output file descriptor.
This lock is set using
fcntl(2)
with the
F_SETLKW
command.
If the output file is already locked,
cat
will block until the lock is acquired.
- -n
-
Number the output lines, starting at 1.
- -s
-
Squeeze multiple adjacent empty lines, causing the output to be
single spaced.
- -t
-
Implies the
-v
option, and displays tab characters as
`^I'
as well.
- -u
-
The
-u
option guarantees that the output is unbuffered.
- -v
-
Displays non-printing characters so they are visible.
Control characters print as
`^X'
for control-X; the delete
character (octal 0177) prints as
`^?'.
Non-ascii characters (with the high bit set) are printed as
`M-'
(for meta) followed by the character for the low 7 bits.
EXIT STATUS
The
cat
utility exits 0 on success, and >0 if an error occurs.
EXAMPLES
The command:
-
cat file1
will print the contents of
file1
to the standard output.
The command:
-
cat file1 file2 > file3
will sequentially print the contents of
file1
and
file2
to the file
file3,
truncating
file3
if it already exists.
See the manual page for your shell (i.e.,
sh(1))
for more information on redirection.
The command:
-
cat file1 - file2 - file3
will print the contents of
file1,
print data it receives from the standard input until it receives an
EOF
(`^D')
character, print the contents of
file2,
read and output contents of the standard input again, then finally output
the contents of
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
cat
when it encountered the first
`-'
operand.
SEE ALSO
head(1),
hexdump(1),
lpr(1),
more(1),
pr(1),
tail(1),
view(1),
vis(1),
fcntl(2)
STANDARDS
The
cat
utility is expected to conform to the
IEEE Std 1003.2-1992 (``POSIX.2'')
specification.
The flags
[-belnstv]
are extensions to the specification.
HISTORY
A
cat
utility appeared in
Version 1 AT&T UNIX
.
Dennis Ritchie designed and wrote the first man page.
It appears to have been
cat(1).
BUGS
Because of the shell language mechanism used to perform output
redirection, the command
``
cat
file1
file2
>
file1
''
will cause the original data in file1 to be destroyed!
This is performed by the shell before
cat
is run.