Exit from child script to parent script with error message

In csh, use

exit [n]

Suppose you want to write a script named readable that returns a 0 if a file is readable and a 1 if the file is not readable.

     if [ -r "$1" ] then
          exit 0
     else 

          exit 1
     endif

You pass readable a single argument, which is a filename. If the file is a readable file, the return code is a 0; otherwise, a 1 is returned. Now in your parent shell you can use the $? ($status-csh) variable to test whether the file is readable are not. For example, your parent shell might look like this:

     readable somefile
     if [ $? ] then
          echo "Processing the file"
          ...
     else 

          echo "Cannot read the file"
     endif

This provides you with the capability to tell whether a child shell script completed with or without errors.

Note: this useful text is from http://alasir.com/