CAT(1) BSD General Commands Manual CAT(1)
cat -- concatenate and print files
cat [-beflnstuv] [-] [file ...]
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.
The cat utility exits 0 on success, and >0 if an error occurs.
will print the contents of file1 to the standard output.
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.
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 con-
tents 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.
head(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.
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.
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).
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.
September 23, 2006 BSD