[Linux] Bash timeout Uso: Limit command execution time

Overview

The timeout command in Bash is used to run a command with a time limit. If the command does not complete within the specified duration, timeout will terminate it. This is particularly useful for preventing long-running processes from hanging indefinitely.

Usage

The basic syntax of the timeout command is as follows:

timeout [options] duration command [arguments]

• duration: The time limit for the command to run, specified in seconds (or with suffixes like m for minutes, h for hours, etc.).
• command: The command you want to run with a time limit.
• arguments: Any arguments that the command may require.

Common Options

• -k, --kill-after=DURATION: After the initial timeout, this option allows you to specify a duration to wait before forcibly killing the command.
• -s, --signal=SIGNAL: Specify the signal to send to the command when the timeout occurs. The default is SIGTERM.
• --preserve-status: Exit with the status of the command instead of the timeout status.

Common Examples

1. Basic usage with a timeout of 5 seconds:

   timeout 5s sleep 10
   

   This command attempts to run sleep 10, but it will be terminated after 5 seconds.

2. Using a different signal:

   timeout -s SIGKILL 3s sleep 10
   

   Here, sleep 10 will be killed with SIGKILL after 3 seconds if it is still running.

3. Preserving the exit status of the command:

   timeout --preserve-status 2s false
   echo $?
   

   This will run false with a timeout of 2 seconds and print the exit status of false, which is 1.

4. Killing after a timeout with a grace period:

   timeout -k 5s 10s sleep 20
   

   This command will allow sleep 20 to run for 10 seconds, then send a SIGTERM. If it does not terminate within 5 seconds, it will be forcibly killed.

Tips

• Always specify a reasonable duration to avoid unintentionally terminating important processes.
• Use --preserve-status when you need to check the exit status of the command after it runs.
• Consider using the -k option if you want to give the command a chance to clean up before being forcibly terminated.