Open navigation menu

Signal Handling and Process Control

Handles Unix signals in Bash scripts using trap, kill, and wait for graceful shutdown, timeout enforcement, and inter-process communication.

BashResilience

Code

snippet
#!/usr/bin/env bash
set -uo pipefail

on_sigterm() {
    echo "Received SIGTERM, shutting down gracefully..."
    exit 0
}

on_sigint() {
    echo "Received SIGINT (Ctrl+C), cleaning up..."
    exit 130
}

on_sigusr1() {
    echo "Received SIGUSR1, reloading configuration..."
}

trap on_sigterm TERM
trap on_sigint INT
trap on_sigusr1 USR1

echo "PID: $$"
echo "Send signals: kill -TERM $$, kill -USR1 $$"

# Run a child process with timeout
run_with_timeout() {
    local timeout=$1
    shift

    "$@" &
    local pid=$!

    (
        sleep "$timeout"
        kill -TERM "$pid" 2>/dev/null
    ) &
    local timer_pid=$!

    wait "$pid" 2>/dev/null
    local status=$?

    kill "$timer_pid" 2>/dev/null
    wait "$timer_pid" 2>/dev/null

    return $status
}

echo "Running with timeout..."
run_with_timeout 3 sleep 10 && echo "Completed" || echo "Timed out or failed"

# Graceful process termination
graceful_kill() {
    local pid=$1
    local timeout=5

    kill -TERM "$pid" 2>/dev/null

    for ((i=0; i<timeout*10; i++)); do
        kill -0 "$pid" 2>/dev/null || return 0
        sleep 0.1
    done

    echo "Process did not exit, sending SIGKILL"
    kill -KILL "$pid" 2>/dev/null
}

echo "Signal handling demo complete"

Related Examples