Background Commands

Source: https://askubuntu.com/questions/510811/what-is-the-difference-between-ctrl-z-and-ctrl-c-in-the-terminal

Note: I found more info on fg in the man page for sh (see man sh).

We all end up pressing Ctrl + Z instead of Ctrl + C one day and not knowing what to do. This isn’t always a big deal unless the program that was running locked some resource you want to use. Closing the terminal “fixes” it but that might be inconvenient. What Ctrl + Z does is suspend the program instead of stopping it like Ctrl + C. So it’s not running but it’s basically paused and in the background.

There are two commands you can use to control programs in the background bg and fg. Didn’t find any info on these programs from a cursory search. No man page for either and --help doesn’t seem to be an argument. The following is from my testing mostly using ping which still sends messages to the terminal even if it’s running in the background. To see if it is in the background I tried using another command like top. From those test I concluded the following:

• fg - brings a suspended (or running in the background) program to the foreground
• bg - resumes a suspended program in the background (you can continue to use the terminal, with the background program possibly sending messages)
• & at the end of command seems to start a command and then put it to run in the background so fg can be used to bring it back to the foreground