CODEWITHSUNDEEP
bashpid
Tzury Bar Yochay
Tzury Bar Yochay

Reputation: 9004

Withing script X getting the PID of the process which feeds the stdin

I want to execute Program_A, and have it output examined by Program_B. e.g.

$ Program_A | Program_B

Within Program_B, I would like to be able to terminate Program_A if a certain condition matched.

I am looking for a way to do this in BASH (have a solution in python with popen).

Also, pidof Program_A and alike are not a good solution since there can be many instances of it and only a particular one shall be terminated.

Upvotes: 0

Views: 114

Answers (2)

Raghuram
Raghuram

Reputation: 3967

You can get the process id of Program_A in the Program_A itself and print that as the first line and other outputs to Program_B. If you do this then you can kill the Program_A with kill call from Program_B

Upvotes: 1

Bartosz Moczulski
Bartosz Moczulski

Reputation: 1239

In Program_B you could close() stdin when you detect the closing condition. It will cause Program_A to receive error upon write() and possibly terminate.

Now, the Program_A may choose to ignore those errors (I don't know if it's your own application or a pre-compiled tool) and here comes the funny part. In Program_B you can examine where does your stdin come from:

my_input=`readlink /proc/$$/fd/0`

then, if it's a something like "pipe:[134414]", find any other process whose stdout equals

case "$my_input" in
  pipe:*)
    for p in /proc/[0-9]*
    do
      if [ "$my_input" = "`readlink $p/fd/1`" ]
      then
        bad_guy=`sed -e 's:.*/::' <<< "$p"`
        echo "Would you please finish, Mr. $bad_guy ?!"
        kill $bad_guy
        break
      fi
    done
    ;;
  *)
    echo "We're good";;
esac

Upvotes: 0

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