getting pid of two last commands executed in background and do stuff

Question

I wrote this bash:

#!/bin/bash

    eval "(a command) &"
    pid1=$!

    eval "(while kill -0 $pid1; do .... ; done) &"  #It creates file.txt after few seconds
    pid2=$!

    if [ -s /tmp/file.txt ]; then
             for line in $(cat /tmp/file.txt)
                 do
                  sth
                 done

With logic of bash scripting: Is the values of pid1 and pid2 correct?

Is this script running correctly?

score 1 · Accepted Answer · answered May 25 '14 at 12:50

1

I do not think you need the `eval "(...) &" syntax. Simply do this instead:

cmd1 &
pid1=$!

cmd2 &
pid2=$!

But otherwise your approach looks OK to me.

Example

$ more ex.bash 
#!/bin/bash

sleep 10 &
pid1=$!

sleep 10 &
pid2=$!

echo "ID1: $pid1 --- ID2: $pid2"

Now when I run it:

$ ./ex.bash 
ID1: 27866 --- ID2: 27867

We can confirm this is correct:

$ pgrep -l sleep
27866 sleep
27867 sleep

answered May 25 '14 at 12:50

slm

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Thank you very much, I used `eval` because my commands are long and quite complicated... – MLSC May 25 '14 at 13:01
So my while loop with the condition `kill -0 $pid1` is correct, isn't it? – MLSC May 25 '14 at 13:02
1

@MortezaLSC - seems reasonable to me. – slm May 25 '14 at 13:24

getting pid of two last commands executed in background and do stuff

1 Answers1

Example