Examples of using `expr'
------------------------
Here are a few examples, including quoting for shell metacharacters.
To add 1 to the shell variable `foo', in Bourne-compatible shells:
foo=`expr $foo + 1`
To print the non-directory part of the file name stored in `$fname',
which need not contain a `/'.
expr $fname : '.*/\(^.*\)' '^|' $fname
An example showing that `\+' is an operator:
expr aaa : 'a\+'
=> 3
expr abc : 'a\(.\)c'
=> b
expr index abcdef cz
=> 3
expr index index a
error--> expr: syntax error
expr index quote index a
=> 0