&

执行程序的后面加&可以将程序转到后台(这个后台是当前会话的后台，并不是守护进程)执行，即$./a.out &,这样我们在打开诸如$gedit test.txt的时候可以写成$gedit test.txt &以防止它占用终端。后台进程也叫后台作业，执行后台进程的时候会有一个后台作业的编号：

$./a.out &
[1] 3054        #后台作业1的编号是3054

jobs

$jobs用来查看当前会话的后台作业(后台进程组):

$./a.out &
[1] 3102
$./a.out &
[2] 3103
$./a.out &
[3] 3104
$./a.out &
[4] 3105
$./a.out &
[5] 3106
161029 $jobs
[1]   Running                 ./a.out &
[2]   Running                 ./a.out &
[3]   Running                 ./a.out &
[4]-  Running                 ./a.out &
[5]+  Running                 ./a.out &

fg

$fg [作业号]可以将后台进程变成前台进程

$fg 1
./a.out
^C
$jobs
[2]   Running                 ./a.out &
[3]   Running                 ./a.out &
[4]-  Running                 ./a.out &
[5]+  Running                 ./a.out &
$fg 2
./a.out
^C
$jobs
[3]   Running                 ./a.out &
[4]-  Running                 ./a.out &
[5]+  Running                 ./a.out &

Ctrl+z bg

Ctrl+z将当前前台的进程在后台挂起，$bg ［任务号］可以将在后台挂起的进程运行起来

$jobs
[3]   Running                 ./a.out &
[4]-  Running                 ./a.out &
[5]+  Running                 ./a.out &
$fg 3
./a.out
^Z
[3]+  Stopped                 ./a.out
161029 $bg 3
[3]+ ./a.out &