CODEWITHSUNDEEP
bashshelldocker
smallbee
smallbee

Reputation: 175

how to wait for "docker exec " to complete before continue in shell script

I have a docker exec command, and I want to wait for it to complete before continuing the rest of a shell script, how do I accomplish that?

#!/bin/bash
docker exec -it debian sleep 10;

wait
echo done

Update: should not use -it option 

#!/bin/bash
docker exec debian sleep 10;

wait
echo done

Upvotes: 2

Views: 11619

Answers (2)

BMitch
BMitch

Reputation: 263469

The docker exec command will wait until it completes by default. The possible reasons for docker exec to return before the command it runs has completed, that I can think of, are:

  1. You explicitly told docker exec to run in the background with the detach flag, aka -d.
  2. The command you are exec'ing inside the container returns before a process it runs has completed, e.g. launching a background daemon. In that scenario, you need to adjust the command you are running.

Here are some examples:

$ # launch a container to test:
$ docker run -d --rm --name test-exec busybox tail -f /dev/null
a218f90f941698960ee5a9750b552dad10359d91ea137868b50b4f762c293bc3

$ # test a sleep command, works as expected
$ time docker exec -it test-exec sleep 10

real    0m10.356s
user    0m0.044s
sys     0m0.040s

$ # test running without -it, still works
$ time docker exec test-exec sleep 10

real    0m10.292s
user    0m0.040s
sys     0m0.040s

$ # test running that command with -d, runs in the background as requested
$ time docker exec -itd test-exec sleep 10 

real    0m0.196s
user    0m0.056s
sys     0m0.024s

$ # run a command inside the container in the background using a shell and &
$ time docker exec -it test-exec /bin/sh -c 'sleep 10 &'

real    0m0.289s
user    0m0.048s
sys     0m0.044s

Upvotes: 4

smallbee
smallbee

Reputation: 175

Update: should not use -it option. This should work.

#!/bin/bash
docker exec debian sleep 10;

wait
echo done

Upvotes: 3

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