Bash, CTRL+C in eval not interrupting the main scr

问题:

In my bash script, I'm running an external command that's stored in $cmd variable. (It could be anything, even some simple bash oneliner.)

If ctrl+C is pressed while running the script, I want it to kill the currently running $cmd but it should still continue running the main script. However, I would like to preserve the option to kill the main script with ctrl+C when the main script is running.

#!/bin/bash
cmd='read -p "Ooook?" something; echo $something; sleep 4 ' 
while true; do
    echo "running cmd.."
    eval "$cmd"     # ctrl-C now should terminate the eval and print "done cmd"
    echo "done cmd"
    sleep 5         # ctrl-C now should terminate the main script
done

Any idea how to do it some nice bash way?

Changes applied based on answers:

#! /bin/bash

cmd='read -p "Ooook1?" something; read -p "Oook2?" ; echo $something; sleep 4 ' 
while true; do
    echo "running cmd.."
    trap "echo Interrupted" INT
    eval "($cmd)"     # ctrl-C now should terminate the eval and print "done cmd"
    trap - INT
    echo "done cmd"
    sleep 5         # ctrl-C now should terminate the main script
done

Now, pressing ctrl+C while "Ooook1?" read will break the eval only after that read is done. (it will interrupt just before "Oook2") However it will interrupt "sleep 4" instantly.

In both cases it will do the right thing - it will just interrupt the eval subshell, so we're almost there - just that weird read behaviour..

回答1:

If you can afford having the eval part run in a subshell, "all" you need to do is trap SIGINT.

#! /bin/bash

cmd='read -p "Ooook1?" something; read -p "Oook2?" ; echo $something; sleep 4 ' 
while true; do
    echo "running cmd.."
    trap "echo Interrupted" INT
    eval "($cmd)"     # ctrl-C now should terminate the eval and print "done cmd"
    trap - INT
    echo "done cmd"
    sleep 5         # ctrl-C now should terminate the main script
done

Don't know if that will fit your specific need though.

$ ./t.sh 
running cmd..
Ooook1?^CInterrupted
done cmd
^C
$ ./t.sh 
running cmd..
Ooook1?qsdqs^CInterrupted
done cmd
^C
$ ./t.sh 
running cmd..
Ooook1?qsd
Oook2?^CInterrupted
done cmd
^C
$ 
GNU bash, version 4.1.9(2)-release (x86_64-pc-linux-gnu)

回答2:

You can determine whether the sleep command exited abnormally by examining the last exit status echo $?. A non-zero status probably indicates Ctrl-C.

回答3:

No, read is not an external command, it is internal builtin bash command being executed in the same process as the other instructions. So at Ctrl-C all the process will be killed.

P.S. Yes. you can execute command in subshell. Something like this

#!/bin/bash
cmd='trap - INT; echo $$; read -p "Ooook?" something; echo $something; sleep 4 ' 
echo $$
while true; do
    echo "$cmd" > tmpfile
    echo "running cmd.."
    trap "" INT
    bash tmpfile
    rm tmpfile  
    trap - INT
    echo "done cmd"
    sleep 5         # ctrl-C now should terminate the main script   
done