Loop in macOS not working

Question

I need to execute the following shell script in my macOS terminal. The loop never executes more than its first iteration.

function execute_function() {
# Launch job
  number_of_jobs=$1
  echo "Launching ${number_of_jobs} jobs"
  for i in {1..$1}; do
    job_id=`head /dev/urandom | tr -dc A-Z0-9 | head -c 6 ; echo ''`
    echo "Launching Job: $job_id"
    echo $i
  done
}

When I run it, I always get:

execute_function 10

    Launching 10 jobs
    Launching Job: XX9BWC
    {1..10}

The same happens if I replace: $1 with $number_of_jobs or "${number_of_jobs}"

Kusalananda · Answer 1 · 2019-04-02T07:59:20.780

9

Your script is written for zsh but you are executing it with bash.

bash does not support using variables as ranges in brace-expansions.

To resolve this, simply arrange for the script or function be executed in a zsh shell (especially if the script is longer than what you are showing and is using other zsh features). This shell is installed by default on macOS as /bin/zsh. You may add #!/bin/zsh as the first line in the script to have it execute with zsh by default.

See also:

edited Apr 02 '19 at 07:59

answered Apr 02 '19 at 05:28

Kusalananda

333,661

1

include #!/bin/zsh as first line. (you may need to check the path. – ctrl-alt-delor Apr 02 '19 at 07:57
what about #!/usr/bin/env zsh? – Jakub Jindra Apr 02 '19 at 08:46
@JakubJindra That would work to, but the default location of zsh is /bin/zsh on macOS. Obviously, you may want to use env if you need to use a 3rd-party installation of zsh. However, this is not the essence of this particular question. – Kusalananda Apr 02 '19 at 08:50

Jakub Jindra · Accepted Answer · 2019-04-02T06:59:39.650

6

The problem here is variable in braces expansion.

Try rewriting it to

for ((i=1;i<=$1;i++))
do
  #your code here
done

edited Apr 02 '19 at 06:59

answered Apr 02 '19 at 05:08

Jakub Jindra

1,462

That worked perfectly – gogasca Apr 02 '19 at 05:22

Loop in macOS not working

2 Answers2