Intro To 'timeout' Command In Linux

2023-11-01 - By Robert Elder

     I use the 'timeout' command, to 'Time Out' a command if it's been running for too long:

timeout 123 ./a.out

Using 'timeout' to 'Time Out' A Process

     Here, I have simple program in the file 'busy-loop-program.c':

int main(){
	while(1){}
	return 0;
}

     If I compile and run this program by itself, it will literally run forever:

gcc busy-loop-program.c -o busy-loop-program
./busy-loop-program

     But if I run this program using the 'timeout' command with a value of 3, the busy loop program will be terminated after 3 seconds:

timeout 3 ./busy-loop-program

Example Use Case Of 'timeout' Command

     Here's an example of a use case for the 'timeout' command that involves synchronizing backups that only transfer during the night time.  Here, I have an rsync command that copies local files to a remote backup server:

/usr/bin/rsync -avvv --progress --append-verify /my-important-files/ remote-backup-server:/backups/my-important-files

     If the files are very large, this could run for multiple days and slow down my network traffic for the entire duration.  I can use the 'timeout' command, with a timeout value of 2 hours:

timeout 2h /usr/bin/rsync -avvv --progress --append-verify /my-important-files/ remote-backup-server:/backups/my-important-files

     Then, I can install the full command as a cron job that runs every morning at 3am:

1 3 * * * timeout 2h /usr/bin/rsync -a --append-verify /my-important-files/ remote-backup-server:/backups/my-important-files

     This way, the backup operation will make a bit of progress every day, and use all of the network capacity between 3 and 5 am.  During the day, I'll have all the network capacity to myself.

     And that's why the 'timeout' command is my favourite Linux command.