Controlling Processes

CTRL+C Interrupting a Process

Many (but not all) command line programs can be interrupted by using CTRL+C.

$ xlogo # 运行 xlogo 后，shell 处于等待 xlogo 结束的状态，此时 Press CTRL+C
^C
$

& Putting a Process in the Background Immediately

$ xlogo &
[1] 8108
$

This message is part of a shell feature called job control. With this message, the shell is telling us that we have started job number 1 ([1]) and that it has PID 28236.

$ ps
 PID TTY              TIME CMD
7288 pts/1 00:00:00 bash
8180 pts/1 00:00:00 xlogo
8120 pts/1 00:00:00 ps

jobs List Jobs

$ jobs
[1]+  Running                        xlogo &

fg Returning a Process to the Foreground

**fg %jobspec**

• If we have only one background job, the jobspec(job numer) is optional.

  $ fg %1
  xlogo

  CTRL+Z Stopping (Pausing) a Process

  **CTRL+Z** does 2 things:

• Stop a process without ternimating it;

• Place the process in the background.

  $ xlogo
  ^Z
  [1]+  Stopped                        xlogo &

  After stopping xlogo program, the xlogo window does not respond to window resizing.

  bg Putting a Process in the Background Manually

  We may use bg to move a process from the foreground to the background If we launch a graphical program from the command line but forget to place it in the background by appending the trailing $.

1. First, stop the program by pressing CTRL+Z;
2. Second, run bg %jobspec
   • As with the fg, If we have only one background job, the jobspec(job numer) is optional.

     $ xlogo # forget the trailing $
     ^Z
     [1]+  Stopped                        xlogo &
     $ bg %1
     $