bash script: parsing grep command output and passing to second action

Question

docker-compose down

sometimes crashes, leaving behind busy resources which prevent fully unmounting and remounting docker volumes

i can manually fix this by doing something like:

grep -l 12c8b1e0d711db12b /proc/*/mountinfo

which gives:

/proc/12053/mountinfo
/proc/16127/mountinfo
...
/proc/16139/mountinfo
/proc/16192/mountinfo

etc

where each number is the process PID now i can do

kill -9 16139 12053 ... 16139

I'm trying to put this into a bash script to help automate this process.

Question: I need to pass the output of grep command through the correct regex to parse out the 2nd argument (the int value in each line of /proc/16192/mountinfo). The I need to assemble these into a space separated string, and finally pass this string as argument to kill.

I'm not really sure how to approach this in bash scripting

Any and all pointers welcomed

apatniv · Accepted Answer · 2018-10-06 02:13:54Z

4

You can use straight up bash scripting with parameter substitution to extract the process id and put them in an array and then use kill on it.

For example:

declare -a process
for t1 in $(grep -l 12c8b1e0d711db12b /proc/*/mountinfo); do
   t2="${t1#/proc/}" # remove /proc/ from beginning
   pid="${t2%/mountinfo}" # remove /mountinfo from the end
   process+=("$pid")
done

kill -9 "${process[@]}"

answered Oct 6, 2018 at 2:13

apatniv

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3 Comments

miken32 Over a year ago

Good approach, can I suggest process+=("${t1//[^[:digit:]]/}") though?

apatniv Over a year ago

Sure. It is better performant and removes the unnecessary creation of temp variables. I would prefer pid="${t1//[^[:digit:]]/}" for the sake of readability instead of doing everything in one line.

baku Over a year ago

seems to work great, and way less complicated than i was expecting. thanks!

Ed Morton · Accepted Answer · 2018-10-07 13:32:43Z

0

Whenever you find yourself wanting to parse the output of grep, sed, etc. you should really consider just using awk instead.

procs=$(awk '/12c8b1e0d711db12b/{split(FILENAME,f,"/"); print f[3]}' /proc/*/mountinfo)
[ -n "$procs" ] && kill -9 "$procs"

answered Oct 7, 2018 at 13:32

Ed Morton

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