[Chapter 46] 46.6 Watch Out for Bourne Shell -e Bug
Author: Jerry Peek, Tim O'Reilly & Mike Loukides
Date: 1998-08-04T21:55:40Z

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| Chapter 46 Shell Script Debugging and Gotchas |

## 46.6 Watch Out for Bourne Shell -e Bug

The Bourne shell -e option should stop execution when a command returns a non-zero status. Does your -e option seem to cause some if commands to abort scripts? If so, you have a copy of the Buggy Bourne Shell, as distributed with 4.2BSD, 4.3BSD, and probably several other systems. It can be identified by running:

>     $ set -e
>     $ if false; then echo yipe; else echo ok; fi

and noting that the shell exits instead of printing `ok`, and by:

    ||
    $ set -e
    $ false || echo ok

which also exits and should not, and by:

>     $ set -e
>     $ while false; do :; done

To fix it, first get the source, and then change it in the obvious three places in xec.c. You will have to learn Bournegol [the ALGOL-like dialect of C that Steve Bourne used to write the original Bourne shell-JP ]. Another alternative is to replace /bin/sh with one of the free sh look-alikes (1.8), provided you can find one that is enough alike.

As a workaround, you can `set +e` around all the tests that might fail. Unfortunately, some versions of the Buggy Bourne Shell do not even support `set +e`; here the only workaround is to run a subshell (38.4) without the -e flag.

- CT in comp.unix.questions on Usenet, 20 February 1990

46.5 Stop Syntax Errors in String Tests |  | 46.7 Quoting and Command-Line Parameters