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Looping over comma-separated values in Bash
Anubhav Gain
2024-03-28
bash
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cli

Looping over comma-separated values in Bash#

Given a file (or a process) that produces comma separated values, here’s how to split those into separate variables and use them in a bash script.

The trick is to set the Bash IFS to a delimiter, then use my_array=($my_string) to split on that delimiter.

Create a text file called data.txt containing this:

first,1
second,2

You can create that by doing:

Terminal window
echo 'first,1
second,2' > /tmp/data.txt

To loop over that file and print each line:

Terminal window
for line in $(cat /tmp/data.txt);
do
  echo $line
done

To split each line into two separate variables in the loop, do this:

Terminal window
for line in $(cat /tmp/data.txt);
do
  IFS=$','; split=($line); unset IFS;
  # $split is now a bash array
  echo "Column 1: ${split[0]}"
  echo "Column 2: ${split[1]}"
done

Outputs:

Column 1: first
Column 2: 1
Column 1: second
Column 2: 2

Here’s a script I wrote using this technique for the TIL Use labels on Cloud Run services for a billing breakdown:

#!/bin/bash
for line in $(
  gcloud run services list --platform=managed \
    --format="csv(SERVICE,REGION)" \
    --filter "NOT metadata.labels.service:*" \
  | tail -n +2)
do
  IFS=$','; service_and_region=($line); unset IFS;
  service=${service_and_region[0]}
  region=${service_and_region[1]}
  echo "service: $service    region: $region"
  gcloud run services update $service \
    --region=$region --platform=managed \
    --update-labels service=$service
  echo
done
Looping over comma-separated values in Bash
https://mranv.pages.dev/posts/looping-over-comma-separated-values-in-bash/
Author
Anubhav Gain
Published at
2024-03-28
License
CC BY-NC-SA 4.0
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