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bashshellgitlab-cigitlab-ci-runner

Why same command fails in GitLab CI?

The following command works perfectly on the terminal but the same command fails in GitLab CI.

echo Hello >> foo.txt; cat foo.txt | grep "test"; [[ $? -eq 0 ]] && echo fail || echo success

return is success but the same command in GitLab CI

$ echo Hello >> foo.txt; cat foo.txt | grep "test"; [[ $? -eq 0 ]] && echo fail || echo success
Cleaning up file based variables
ERROR: Job failed: command terminated with exit code 1

is simply failing. I have no idea why. echo $SHELL return /bin/bash in both.

Solution

  • Source of the issue

    The behavior you observe is pretty standard given the "implied" set -e in a CI context.

    To be more precise, your code consists in three compound commands:

    echo Hello >> foo.txt
cat foo.txt | grep "test"
[[ $? -eq 0 ]] && echo fail || echo success

    And the grep "test" command returns a non-zero exit code (namely, 1). As a result, the script immediately exits and the last line is not executed.

    Note that this feature is typical in a CI context, because if some intermediate command fails in a complex script, we'd typically want to get a failure, and avoid running the next commands (which could potentially be "off-topic" given the error).

    You can reproduce this locally as well, by writing for example:

    bash -e -c "
echo Hello >> foo.txt
cat foo.txt | grep "test"
[[ $? -eq 0 ]] && echo fail || echo success 
"

    which is mostly equivalent to:

    bash -c "
set -e
echo Hello >> foo.txt
cat foo.txt | grep "test"
[[ $? -eq 0 ]] && echo fail || echo success 
"

    Relevant manual page

    For more insight:

    How to fix the issue?

    You should just adopt another phrasing, avoiding [[ $? -eq 0 ]] a-posteriori tests. So the commands that may return a non-zero exit code without meaning failure should be "protected" by some if:

    echo Hello >> foo.txt
if cat foo.txt | grep "test"; then
  echo fail
  false  # if ever you want to "trigger a failure manually" at some point.
else
  echo success
fi

    Also, note that grep "test" foo.txt would be more idiomatic than cat foo.txt | grep "test" − which is precisely an instance of UUOC (useless use of cat).