Linux administration

• Most shells offer job control
  • The ability to stop, restart, and background a running process
• The shell lets you put & on the end of a command line to start it in the background
• Or you can hit Ctrl+Z to suspend a running foreground job
• Suspended and backgrounded jobs are given numbers by the shell
• These numbers can be given to shell job-control built-in commands
• Job-control commands include jobs, fg, and bg

• The jobs builtin prints a listing of active jobs and their job numbers:

$ jobs
[1]- Stopped
[2]
Running
[3]+ Stopped

vim index.html
firefox &
man ls

• Job numbers are given in square brackets
  • But when you use them with other job-control builtins, you need to write them with percent signs, for example %1
• The jobs marked + and - may be accessed as %+ or %- as well as by number
  • %+ is the shell's idea of the current job — the most recently active job
  • %- is the previous current job

• Brings a backgrounded job into the foreground
• Re-starts a suspended job, running it in the foreground
• fg %1 will foreground job number 1
• fg with no arguments will operate on the current job

• Re-starts a suspended job, running it in the background
• bg %1 will background job number 1
• bg with no arguments will operate on the current job
• For example, after running gv and suspending it with Ctrl+Z, use bg to start it running again in the background

• a. Start a process by running man bash and suspend it with Ctrl+Z.
• b. Run xclock in the background, using &.
• c. Use jobs to list the backgrounded and stopped processes.
• d. Use the fg command to bring man into the foreground, and quit from it as normal.
• e. Use fg to foreground xclock, and terminate it with Ctrl+C.
• f. Run xclock again, but this time without &. It should be running in the foreground (so you can't use the shell). Try suspending it with Ctrl+Z and see what happens. To properly put it into the background, use bg.