CODEWITHSUNDEEP
linuxbashshell
Sozed
Sozed

Reputation: 31

Bash Script - How take a result of command and use it

I would like to know how to do this, if for example, when executing a command in a script, retrieve the message linked to this command. For example "AZERTY already exists, please check the error" is the message that comes out after a command (wrong), how do I so that if my BASH script sees this info, tell it to stop the script?

Upvotes: 0

Views: 96

Answers (3)

William Pursell
William Pursell

Reputation: 212178

You almost certainly should not check the error message. Instead just do:

cmd || exit

If cmd fails and writes the message "AZERTY already exists, please check the error" to stderr, then that message will appear and the script will exit with whatever non-zero value cmd exited with. Some commands return non-zero values that have meaning, and you may want to suppress that (for consistent return values from your script) or change that with something like:

cmd || exit 1

On the other hand, if cmd is poorly written and returns a zero value when it "fails" (I'm putting that in quotes since a reasonable definition of "fail" is "return non-zero"), then that is a bug in cmd which should be fixed.

Upvotes: 3

nullUser
nullUser

Reputation: 1833

I recommend using strict mode in all your bash scripts. http://redsymbol.net/articles/unofficial-bash-strict-mode/

Basically put this at the top

#!/bin/bash
set -euo pipefail
IFS=$'\n\t'

The option you specifically asked about is -e

The set -e option instructs bash to immediately exit if any command [1] has a non-zero exit status. You wouldn't want to set this for your command-line shell, but in a script it's massively helpful. In all widely used general-purpose programming languages, an unhandled runtime error - whether that's a thrown exception in Java, or a segmentation fault in C, or a syntax error in Python - immediately halts execution of the program; subsequent lines are not executed.

Upvotes: 1

Chankey Pathak
Chankey Pathak

Reputation: 21666

if ./command | grep -q 'AZERTY already exists, please check the error'; then
  echo "Error found, exiting"
  exit 1
fi

Upvotes: 0

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