Depending on the Bourne shell version you have, the error messages
it gives can be downright useless.
For instance, it can just say
Start your script like this:
(or, if your UNIX can't handle
Note that the shell reads an entire loop ( for , while , etc.) before it executes any commands in the loop.
If you want to run a script with debugging but you don't want to edit the script file, you can also start the shell explicitly from the command line and give the options there:
Debugging output is usually pretty long, more than a screenful. So I pipe it to a pager like pg . But the shell sends its debugging output to stderr , so I . Using a pager has another advantage: if you want to kill the script before it finishes, just use the pager's "quit" command (like q ). When the pager quits, UNIX may even kill the shell script (you may see the message ).
If the script is slow, you can run it in the background. into a . Use to "watch" the log file. If you want to do something else while the script runs, just kill the tail command (with CTRL-c or your interrupt key), do something else, then start another tail -f when you want to watch again.
Finally, if the script normally writes something to its standard output, you can.
If the shell says
If you're getting an
echo "DEBUG: quitting early..." 1>&2 exit
Then run your script.
Those lines will print a message and stop the shell where you put them.
If you don't get the
A message like
The shell may give you an error that mentions "line 1" or another line number that seems way too small, when there's no error close to the top of your script. Look at any loops or other structures with . Some Bourne shells start a separate shell to run these loops and lose track of the line numbers.