Predefined variables

The C-shell has some predefined variables. We've already met argv. The most useful other ones are listed below.

Shell variable	Meaning
cwd	Current working directory
home	Home directory
path	List of directories in which to search for commands
status	The status returned by the last command, where 0 means a successful completion, and a positive integer indicates an error, the higher the value, the higher the severity.
user	Username

So if you wanted to include details of the user and directory at the head of some data-processing log you might write this in your script.

     % echo "Processed by:        $user" > logfile
     % echo "Directory processed: $path" >> logfile

This writes a heading into file logfile saying who ran the script, and then appends details of the directory in which processing occurred. Note the different metacharacters, namely > redirects the output to a file, and » appends to an existing file.