Bash script to exit when any command (including non-simple commands) fail

Question

I have a script

#! /bin/sh
set -eux

command_a

command_b | command_c

while [ true ]; do
    command_d
done

I'd like this to fail when any command fails. If command_a fails, the script fails, but if command_b or command_d (not sure about command_c) fail, the script carries on.

I'd strongly suggest saying while true; do instead of while [ true ]; do -- the latter implies that while [ false ]; do would behave differently, which it doesn't. — Charles Duffy
– Charles Duffy, Commented Dec 13, 2017 at 20:15

Ashutosh Bharti · Accepted Answer · 2017-12-13 20:10:55Z

5

This should not happen if you are using set -eux, may be I can tell better if I knew the actual command. One way to achieve exiting can be to use ||

while [ true ]; do
    command_d || exit 1
done

a || b means "do a (completely). If it didn't succeed, do b"

Also, you should use set -euxo pipefail

Refer this: https://vaneyckt.io/posts/safer_bash_scripts_with_set_euxo_pipefail/

answered Dec 13, 2017 at 20:10

Ashutosh Bharti

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3 Comments

Charles Duffy Over a year ago

I strongly disagree with the characterization of set -e as "safe". See the exercises in BashFAQ #105 (below the allegory), and the list of incompatibilities between different shells' implementations of set -e at in-ulm.de/~mascheck/various/set-e. Because bash has no way to distinguish between a command correctly returning an exit status that indicates a false result of a test and an exit status indicating an error, set -e's behavior is necessarily full of heuristics that try to guess among the cases.

Charles Duffy Over a year ago

...among these heuristics is maintaining the "checked" flag to determine whether an operation is considered part of a test or conditional -- its behavior, particular in the context of function calls or compound commands, is almost universally misunderstood.

Charles Duffy Over a year ago

(set -u is not nearly as bad as set -e, but similarly, it tends to break otherwise correct code not explicitly written for compatibility; consequently, pipefail is the only part of this advice that isn't controversial at all... though even then, its use occasionally leads to surprises).

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