How to handle ctrl+c in a shell script?

#include <stdio.h> int main() { while(1) { int n1,n2; printf("Enter the first number\n"); scanf("%d",&n1); printf("Enter the second number\n"); scanf("%d",&n2); printf("Entered number are n1 = %d , n2 =%d\n",n1,n2); } }

#/i/bin/sh echo run the hello binary ./hello < in.txt & trap_ctrlc() { ps -eaf | grep hello | grep -v grep | awk '{print $2}' | xargs kill -9 echo trap_ctrlc exit } trap trap_ctrlc SIGHUP SIGINT SIGTERM

Enter the first number Enter the second number Entered number are n1 = 1 , n2 =2 Enter the first number Enter the second number Entered number are n1 = 1 , n2 =2 Enter the first number Enter the second number Entered number are n1 = 1 , n2 =2

Change your c program so it checks if reading data actually succeeded:

#include <stdio.h>

int main()
{
    int n1,n2;
    while(1) {
        printf("Enter the first number\n");
        if(scanf("%d",&n1) != 1) return 0;   /* check here */
        printf("Enter the second number\n");
        if(scanf("%d",&n2) != 1) return 0;   /* check here */
        printf("Entered number are n1 = %d , n2 =%d\n",n1,n2);
    }
}

It will now terminate when the input from in.txt is depleted.

To make something that reads from in.txt many times, you could create a loop in your bash script that feeds ./hello forever (or until it's killed).

Example:

#!/bin/bash

# a function to repeatedly print the content in "in.txt"
function print_forever() {
    while [ 1 ];
    do
        cat "$1"
        sleep 1
    done
}

echo run the hello binary
print_forever in.txt | ./hello &
pid=$!
echo "background process $pid started"

trap_ctrlc() {
    kill $pid
    echo -e "\nkill=$? (0 = success)\n"
    wait $pid
    echo "wait=$? (the exit status from the background process)"
    echo -e "\n\ntrap_ctrlc\n\n"
}

trap trap_ctrlc INT

# wait for all background processes to terminate
wait

Possible output:

$ ./hello.sh
run the hello binary
background process 262717 started
Enter the first number
Enter the second number
Entered number are n1 = 1 , n2 =2
Enter the first number
Enter the second number
Entered number are n1 = 1 , n2 =2
Enter the first number
^C
kill=0 (0 = success)

wait=143 (the exit status from the background process)


trap_ctrlc

Another option can be to kill the child after the wait is interrupted:

#!/bin/bash

function print_forever() {
    while [ 1 ];
    do
        cat "$1"
        sleep 1
    done
}
 
echo run the hello binary
print_forever in.txt | ./hello &
pid=$!
echo "background process $pid started"
 
trap_ctrlc() {
    echo -e "\n\ntrap_ctrlc\n\n"
}
 
trap trap_ctrlc INT
 
# wait for all background processes to terminate
wait
echo first wait=$?
kill $pid
echo -e "\nkill=$? (0 = success)\n"
wait $pid
echo "wait=$? (the exit status from the background process)"`
``

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