1

I am writing a shell script to interact with our local Docker repo and have found that I get different results from my bash script than I expect. First, from the command line using:

des@dev: docker images | grep gateway

I get:

test-gateway 4.27.0-1.5.2-301 b215d109c627 8 days ago 1.977 GB test-gateway dev b215d109c627 8 days ago 1.977 GB test-gateway staging b215d109c627 8 days ago 1.977 GB test-gateway 4.26.2-1.5.2-298 7376dd26db6e 2 weeks ago 2.117 GB test-gateway 4.26.2-1.5.2-297 c84e6de5a18e 2 weeks ago 2.117 GB test-gateway 4.26.0-1.5.2-296 e6a772c0e230 2 weeks ago 2.048 GB test-gateway 4.24.3-1.5.2-295 d3743f5246f4 3 weeks ago 1.978 GB test-gateway prod d3743f5246f4 3 weeks ago 1.978 GB test-gateway 4.24.1-1.5.2-294 99065a070172 5 weeks ago 1.908 GB test-gateway 4.24.1-1.5.2-293 90639b86573a 5 weeks ago 1.908 GB test-gateway 4.24.1-1.5.2-292 223f8c3a41cf 5 weeks ago 1.908 GB test-gateway 4.24.0-1.5.2-291 5646792848cf 6 weeks ago 1.873 GB test-gateway 4.24.0-1.5.2-290 8a4e92f6a7b9 6 weeks ago 1.847 GB test-gateway 4.24.0-1.5.2-289 475e72c8691e 6 weeks ago 1.847 GB test-gateway 4.23.8-1.5.2-288 1c83a9f9ccc4 7 weeks ago 1.812 GB test-gateway 4.23.8-1.5.2-287 5e77c056c703 7 weeks ago 1.812 GB test-gateway 4.23.7-1.5.2-286 b9d9f95ec17d 7 weeks ago 1.812 GB test-gateway 4.23.6-1.5.2-282 f40fe68c0183 8 weeks ago 1.997 GB

Running the following script:

#!/bin/bash docker images | grep gateway | while read line; do read line echo "$line" done;

Returns:

test-gateway staging b215d109c627 8 days ago 1.977 GB test-gateway 4.26.2-1.5.2-298 7376dd26db6e 2 weeks ago 2.117 GB test-gateway 4.26.0-1.5.2-296 e6a772c0e230 2 weeks ago 2.048 GB test-gateway prod d3743f5246f4 3 weeks ago 1.978 GB test-gateway 4.24.1-1.5.2-293 90639b86573a 5 weeks ago 1.908 GB test-gateway 4.24.0-1.5.2-291 5646792848cf 6 weeks ago 1.873 GB test-gateway 4.24.0-1.5.2-289 475e72c8691e 6 weeks ago 1.847 GB test-gateway 4.23.8-1.5.2-287 5e77c056c703 7 weeks ago 1.812 GB test-gateway 4.23.6-1.5.2-282 f40fe68c0183 8 weeks ago 1.997 GB

Why doesn't the bash script return all of the matching rows?

NOTE: Just looking at the output I see it appears the script is somehow doing away with lines where the sizes of the images are the same - which makes this even stranger as there is nothing limiting the output in the script.

Improve this question
1
  • 1
    Not related to the question, just note, instead of pipe, sometimes is better to write: while read ... done < <(docker images | grep gateway) Commented Dec 5, 2017 at 21:35

1 Answer 1

Reset to default
4

You have an extra read line call that is making you skip each line of the results as you parse the output, which needs to be removed.

Also remove an extra layer of sub-shell processing by introducing a simple process-substitution syntax with a read command and while-loop. The syntax basically allows you read from the command output as if it were reading from a file.

while IFS= read -r line; do printf '%s\n' "$line" done< <(docker images | grep gateway)
Improve this answer
Sign up to request clarification or add additional context in comments.

2 Comments

smacks forehead smartly! Thanks @Inian - I surely missed that!
@JayBlanchard: It happens ;)

Start asking to get answers

Find the answer to your question by asking.

Ask question

Explore related questions

See similar questions with these tags.