shell script (busybox) doesn't work as expected on docker container

Question

Running an image based alpine with busybox and ash:

/mnt/builddir/code/src/main/helm # busybox | head -1
BusyBox v1.31.1 () multi-call binary.

I wrote an sh script that prints file's names only if they start with prefix "values", but something with the "if" condition does not work well. This is my script:

for f in ./*
do
  echo ${f##*/}
  if ${f##*/} == 'values'*; then
      echo $f
  fi
done

output:

/mnt/builddir/code/src/main/helm # ./script.sh
Chart.yaml
./script.sh: line 4: Chart.yaml: not found
script.sh
./script.sh: line 4: script.sh: not found
values-feature.yaml
./script.sh: line 4: values-feature.yaml: not found
values-int.yaml
./script.sh: line 4: values-int.yaml: not found
values-prod.yaml
./script.sh: line 4: values-prod.yaml: not found
values-stg.yaml
./script.sh: line 4: values-stg.yaml: not found
values.yaml
./script.sh: line 4: values.yaml: not found

before I changed the code to the above, the if condition looked like that:

if [[ ${f##*/} == values* ]]
then
    ...

But this doesn't work either.

Thanks for you suggestions...

Your question contradicts itself: You tag it as bash, but in the title you write "sh". For bash, [[ ${f##*/} == values* ]] would make sense; for sh obviously not. Also, does not work well and doesn't work either is anecdotal evidence, but not a problem description. — user1934428
– user1934428, Commented Apr 14, 2021 at 10:46

David Maze · Accepted Answer · 2021-04-14 10:47:23Z

1

There are two obvious problems in this script: in your if line you're not invoking test(1) but instead are directly trying to run each file; and the test(1) == operator only does exact string comparisons and not glob or regex matches.

You could use the shell case statement to match a variable against a glob:

case "$f" in
  */values*)
    echo "$f"
    ;;
esac

But the shell for statement can iterate over a glob expansion, and that will be a generally simpler setup:

for f in values*; do
  echo "$f"
done

(This is not at all specific to Docker, and I'd expect you'd get very similar errors running the script directly on the host. You might find it much easier to develop and debug the script without having Docker as an isolation layer between you and the code you're trying to fix.)

answered Apr 14, 2021 at 10:47

David Maze

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2 Comments

jrz Over a year ago

in your 1st example you close brackets /values) but not open. Is that purposely?

Jetchisel Over a year ago

@I.zv, that is the case syntax, see help case

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