3c3
< #  "subst", a script that substitutes one pattern for
---
> #  subst.sh: a script that substitutes one pattern for
5c5,6
< #+ i.e., "subst Smith Jones letter.txt".
---
> #+ i.e., "sh subst.sh Smith Jones letter.txt".
> #                     Jones replaces Smith.
8c9
< E_BADARGS=65   # Wrong number of arguments passed to script.
---
> E_BADARGS=85   # Wrong number of arguments passed to script.
11d11
< # Test number of arguments to script (always a good idea).
29,30d28
< #  Here is where the heavy work gets done.
< 
31a30
> #  Here is where the heavy work gets done.
37c36
< #  The "g", or global flag causes substitution for *every*
---
> #  The 'g,' or global flag causes substitution for EVERY
39c38
< #  Read the literature on 'sed' for an in-depth explanation.
---
> #  Read the 'sed' docs for an in-depth explanation.
41c40
< exit 0    # Successful invocation of the script returns 0.
---
> exit $?  # Redirect the output of this script to write to a file.