Command Line Input and Output Redirection

Computer History Notes - Herong's Tutorial Notes

∟1978 - The C Shell Developed by Bill Joy

∟Command Line Input and Output Redirection

This section provides a quick introduction of C shell command line standard input and output redirection.

C Shell Command Line Input and Output Redirection: Changes input and/or output from terminal console to other commands or files.

Input and output redirection uses the following formats:

command > file - Redirects the standard output of the command to a file. If the file exists, it will be replaced. If the file does not exist, it will be created.
command >> file - Appends the standard output of the command to a file. If the file exists, command output will be appended to the end of the file. If the file does not exist, it will be created.
command < file - Takes a file as the standard input of the command. If the file exists, its content will be read in as standard input. If the file does not exist, the command will fail.
command | another command - Connects the standard output of the first command to the standard input of the second command.
... >&, >>&, and |& ... - Merge standard error output into the standard output.

Examples of C shell command line input and output redirection:

>csh
%ls -al > file list
%more file list
drwx--x--x   6 herong   users        1024 Jul 21 21:56 .
drwxr-xr-x   4 root     root         1024 May 24 22:03 ..
-rw-r--r--   1 herong   users         242 Jul 21 21:56 .cshrc
-rw-r--r--   1 herong   users          76 Jan  4 03:15 .login
-rwxr-xr-x   1 herong   users        3992 Aug 19 10:19 a.out
-rw-r--r--   1 herong   users           0 Jul 21 20:27 file list
-rw-r--r--   1 herong   users          40 Aug 19 10:18 hello.c
-rw-r--r--   1 herong   users           0 Jul 21 21:56 new file
%tar -cO * | compress > backup.tar.Z
%ls -l
-rwxr-xr-x   1 herong   users        3992 Aug 19 10:19 a.out
-rw-r--r--   1 herong   users        2677 Jul 22 20:28 backup.tar.Z
-rw-r--r--   1 herong   users         376 Jul 22 20:27 file list
-rw-r--r--   1 herong   users          40 Aug 19 10:18 hello.c
-rw-r--r--   1 herong   users           0 Jul 21 21:56 new file
%uncompress -c backup.tar.Z | tar -t
a.out
file list
hello.c
new file