CODEWITHSUNDEEP
bashdockershellescaping
ataraxis
ataraxis

Reputation: 1582

pass an argument with escape characters to a script with docker exec

I would like to pass the variable $styled to a script inside a docker container.

The docker command would look something like

docker exec container_name "/bin/bash -c cd /where/the/script/is && ./echo.sh $styled"

the echo.sh would look like this

#!/bin/bash
echo -e $1

the variable $styled contains escape characters, so lets say it is:

styled=$'\e[7mSOME_TEXT\e[27m'

On my local computer i can pass the variable to a local echo.sh without any issues, unfortunately it doesn't work while using dockers exec.

the error message is something like:

./echo.sh \x1b[7mFF1SOME_TEXT\x1b[27m: no such file or directory": unknown

I am pretty sure it has to do with how escaping works, single quotes, double quotes and so on, but I am simply confused by all those layers.

I also tried:

docker exec container_name "/bin/bash -c 'cd /where/the/script/is && ./echo.sh '$P'"

which results in

stat /bin/bash -c 'cd /where/the/script/is && ./echo.sh '\x1b[7mSOME_TEXT\x1b[27m': no such file or directory"

Upvotes: 0

Views: 5321

Answers (1)

tripleee
tripleee

Reputation: 189628

The argument to bash -c needs to be quoted.

docker exec container_name /bin/bash -c "cd /where/the/script/is && ./echo.sh '$styled'"

The code you exhibit doesn't do anything useful with the cd; if your real code cares which directory it's invoked from, maybe refactor it so it doesn't. Then this is suddenly much simpler.

docker exec container_name /where/the/script/is/echo.sh "$styled"

Still you need to fix the quoting in echo.sh, too:

#!/bin/bash
echo -e "$1"

or perhaps better yet

#!/bin/bash
echo -e "$@"

Maybe you still need docker -it to get output back.

The single quotes in the first snippet above are brittle, and will fail if $styled contains an unescaped literal single quote. If you genuinely need to pass in complex quoted strings to bash -c, maybe do someting like

docker exec container_name /bin/bash -c 'cd /where/the/script/is && ./echo.sh "$1"' -- "$styled"

Passing in literal terminal escape codes is dubious, but I guess trying to fix that antipattern is a lost cause. Maybe at least I could convince you to use printf instead of echo -e?

Upvotes: 2

Related Questions