Grep output split for docker application

Question

I learn about Docker for service hosting. I want to split the desired line somehow to obtain a desired token. In case the token corresponds to CONTAINER_ID, I would split the line in spaces and obtain the first token. I do not even know to start this shell pipe, but it seems useful for every SRE developer. :-)

I tried the command below:

docker ps -a | grep -w <image-name> | head -n1 | awk '{print $1;}'

The output below corresponds to command run docker ps -a.

CONTAINER ID   IMAGE                         COMMAND                  CREATED         STATUS         PORTS                                       NAMES
0e7e52667c2e   sappio-1                      "docker-entrypoint.s…"   3 minutes ago   Up 3 minutes   0.0.0.0:8080->8080/tcp, :::8080->8080/tcp   hardcore_panini
d9cd1a9d2c37   eclipse-mosquitto:2-openssl   "/docker-entrypoint.…"   2 weeks ago     Created                                                    cedalo_platform_mosquitto_1
96f65f3e8bd8   postgres:14.5                 "docker-entrypoint.s…"   3 weeks ago     Up 4 hours                                                 tests_db
bdb51a386349   nginxproxy/nginx-proxy        "/app/docker-entrypo…"   5 months ago    Created                                                    dreamy_bouman

please update the question with any code you've tried, the (wrong) output generated by your code, and the (correct) expected output ... making sure all outputs correspond with the sample input — markp-fuso, Oct 21 '22 at 17:42
still need more details ... an example (or 2) of `` plus the expected/corresponding output — markp-fuso, Oct 21 '22 at 17:46
if using `awk` then there's usually no need for `grep` and/or `head` — markp-fuso, Oct 21 '22 at 18:01

score 0 · Accepted Answer · answered Oct 21 '22 at 17:51

0

FWIW, I often use the following few commands:

img=$(docker image ls | grep some_keyword | head -1 | awk '{print $3}') && echo "image is $img"

docker run -it $img

cont=$(docker ps | tail +2 | head -1 | awk '{print $1}') && echo "container is $cont"

The keyword would be something unique about the name of your image.

answered Oct 21 '22 at 17:51

Pierre D

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A much better approach is to use the `--filter` option to specify how to search for a specific image. The second duplicate is about one scenario where this could sometimes fail (truncated output). – tripleee Oct 21 '22 at 17:55

score 0 · Answer 2 · answered Oct 21 '22 at 17:55

Assumptions:

need to search for an IMAGE or a partial IMAGE
if/when an IMAGE match is found then display the corresponding CONTAINER ID and exit (ie, only interested in the first match)

Using docker.ps.out to simulate the docker/ps output, and adding a few (bogus) lines:

$ cat docker.ps.out
CONTAINER ID   IMAGE                         COMMAND                  CREATED         STATUS         PORTS                                       NAMES
0e7e52667c2e   sappio-1                      "docker-entrypoint.s…"   3 minutes ago   Up 3 minutes   0.0.0.0:8080->8080/tcp, :::8080->8080/tcp   hardcore_panini
d9cd1a9d2c37   eclipse-mosquitto:2-openssl   "/docker-entrypoint.…"   2 weeks ago     Created                                                    cedalo_platform_mosquitto_1
96f65f3e8bd8   postgres:14.5                 "docker-entrypoint.s…"   3 weeks ago     Up 4 hours                                                 tests_db
bdb51a386349   nginxproxy/nginx-proxy        "/app/docker-entrypo…"   5 months ago    Created                                                    dreamy_bouman
001234abcdef   postgres:14.5                 "docker-entrypoint.s…"   3 weeks ago     Up 4 hours                                                 tests_db
9999000aabbc   postgres:14.5                 "docker-entrypoint.s…"   3 weeks ago     Up 4 hours                                                 tests_db

One awk idea:

cat docker.ps.out | awk -v img="post" '
FNR>1 && index($2,img) {print $1; exit}'    # skip header record and if img found in 2nd field then print 1st field and exit the script

For -v img="post":

96f65f3e8bd8

For -v img="proxy":

bdb51a386349

For -v img="XXX":

-- no output == no match

OP's current code uses grep -w to indicate a need for an exact match on the IMAGE field so a small change to our awk script:

cat docker.ps.out | awk -v img="post" '
FNR>1 && $2==img {print $1; exit}'    # skip header record and if 2nd field == img then print 1st field and exit the script

For img="postgres:14.5":

96f65f3e8bd8

For img=postgres:17.2":

-- no output == no match

Grep output split for docker application

2 Answers2