C shell built-in commands
Built-in commands are run within the shell. If a built-in command occurs as any component of a pipeline, except the last, the command runs in a subshell.
Note: If you enter a command from the C shell prompt, the system searches for a built-in command first. If a built-in command does not exist, the system searches the directories specified by the path shell variable for a system-level command. Some C shell built-in commands and operating system commands have the same name. However, these commands do not necessarily work the same way. For more information on how the command works, check the appropriate command description.
If you run a shell script from the shell, and the first line of the shell
script begins with
the C shell runs the shell specified in the comment to process the script.
Otherwise, it runs the default shell (the shell linked to /usr/bin/sh).
If run by the default shell, C shell built-in commands might not be recognized.
To run C shell commands, make the first line of the script #!/usr/bin/csh.