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Comment: Why doesn't set -e (set -o errexit) do what I expected?
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| <<Anchor(faq105)>> == Why doesn't set -e (set -o errexit) do what I expected? == `set -e` was an attempt to add "automatic error detection" to the shell. Its ''goal'' was to cause the shell to abort any time an error occurred, so you don't have to put `|| exit 1` after each important command. That goal is non-trivial, because many commands are ''supposed'' to return non-zero. For example, {{{ if [ -d /foo ]; then ... else ... fi }}} If the `[ -d /foo ]` command triggers the `set -e` abort when it returns non-zero (because the directory does not exist -- a case our script wants to handle in the `else` part), then obviously `set -e` isn't very useful. So the implementors decided to make a bunch of special rules, like "commands that are part of an `if` test are immune", or "commands in a pipeline, other than the last one, are immune". These rules are extremely convoluted. Worse, they ''change'' from one Bash version to another, as Bash attempts to track the extremely slippery POSIX definition of this "feature". When a SubShell is involved, it gets worse still. The behavior changes depending on whether Bash is invoked in POSIX mode. [[http://fvue.nl/wiki/Bash:_Error_handling|Another wiki]] has a page that covers this in more detail. Be sure to check the caveats. GreyCat's personal recommendation is simple: don't use it. Add your own explicit error checking instead. |
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