Stop command without pressing Ctrl+C (No luck using trap function)

Question

I am trying to make a script that runs 2 commands in a for loop as can be seen below:

#!/bin/bash
for ((i=0; i<2; i++)); do
    sudo ./bin/llc test-rx -c 184 
    sleep 5
    trap ctrl_c INT
function ctrl_c() 
{
  echo "Trap: CTRL+C received, exit"
  exit
}
    sudo ./bin/llc rxphylast  
done

The 1st command (test-rx) continues to run as its is executed and it is stopped by pressing Ctrl+C. I want to stop this command in bash script so I used trap function as can be seen in the code. But when I execute the script, 1st command is running until I press Ctrl+C and then 2nd command (rxphylast) executes. So, in my case trap function is not working. Any advice on how to stop the 1st command in the script?

Answer 1

1. Define the function and set the trap outside of the loop
2. Define the function before you use it.

Try:

#!/bin/bash
function ctrl_c() (

{
  echo "Trap: CTRL+C received, exit"
  exit
}

trap ctrl_c INT

for ((i=0; i<2; i++)); do
    sudo ./bin/llc test-rx -c 184 
    sleep 5

    sudo ./bin/llc rxphylast  
done

Another example, not using ./bin/llc:

#!/bin/bash

function ctrl_c()
{
  echo "Trap: CTRL+C received, exit"
  exit
}

trap ctrl_c INT

for ((i=0; i<2; i++)); do
    echo first program
    sudo find / -type f > /dev/null
    sleep 5

    echo second program
    sudo find / -type f > /dev/null
done

Press Ctrl-C while the first find is running and it will print the "Trap: CTRL+C received, exit" message and exit immediately. Press Ctrl-C while the second find is running and it will do the same. This works the same whether sudo is used with the find commands or not - I only put that in there to make sure it wasn't sudo trapping and eating the Ctrl-C.

This is what happens when you run it and press Ctrl-C while the first find is running:

$ ./trap.sh 
first program
^CTrap: CTRL+C received, exit
$