CAT(1) BSD General Commands Manual CAT(1)NAMEcat — concatenate and print files
SYNOPSIScat [-beflnstuv] [-] [file ...]
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 stan‐
dard 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 ALSOhead(1), hexdump(1), lpr(1), more(1), pr(1), tail(1), view(1), vis(1),
fcntl(2)
Rob Pike, "UNIX Style, or cat-v Considered Harmful", USENIX Summer
Conference Proceedings, 1983.
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 redirect‐
ion, 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.
BSD September 23, 2006 BSD
