背景
有時我們運行某個任務，需要保證任務不占據終端影響其他作業，或者保證當前session退出后，任務依然可以繼續運行。
方案
- command &
- nohup command &
- CTRL+Z;bg %n; disown %n
- setsid command
使用方法
command &
該方法可以使任務放在后臺執行，從而不影響當前終端其他作業，但是如果當前終端退出，也會導致后臺任務接收到SIGHUP信號并退出。
-rwx------. 1 Appmanager devops 69 Jun 19 06:07 findBigFiles.bash
[appmanager@localhost toutiao]$ cat findBigFiles.bash
#! /bin/bash
sleep 1m
find $HOME -size +10M | xargs ls -l --block-size=M
[appmanager@localhost toutiao]$ ./findBigFiles.bash > output.log &
[1] 2644
## 退出當前終端，新開終端并查看進程
[appmanager@localhost ~]$ ps -fu appmanager
UID PID PPID C STIME TTY TIME CMD
appmana+ 2769 2768 0 06:08 pts/0 00:00:00 -bash
appmana+ 2818 2769 0 06:08 pts/0 00:00:00 ps -fu appmanager
## 重新后臺執行程序
[appmanager@localhost toutiao]$ ps -fu appmanager
UID PID PPID C STIME TTY TIME CMD
appmana+ 2769 2768 0 06:08 pts/0 00:00:00 -bash
appmana+ 2889 2769 0 06:11 pts/0 00:00:00 /bin/bash ./findBigFiles.bash
appmana+ 2890 2889 0 06:11 pts/0 00:00:00 sleep 1m
appmana+ 2891 2769 0 06:12 pts/0 00:00:00 ps -fu appmanager
[appmanager@localhost toutiao]$ ps -fu appmanager
UID PID PPID C STIME TTY TIME CMD
appmana+ 2769 2768 0 06:08 pts/0 00:00:00 -bash
appmana+ 2906 2769 0 06:13 pts/0 00:00:00 ps -fu appmanager
[1]+ Done ./findBigFiles.bash > output.log
[appmanager@localhost toutiao]$ cat output.log
-rw-------. 1 appmanager devops 35M May 28 19:06 /home/appmanager/.cache/pip/http/d/6/1/f/e/d61fe4b09676f0692c240e67193e3af065d7b9e72f8577595151e51f
-rw-r--r--. 1 appmanager devops 11M May 16 08:49 /home/appmanager/mnt/ansible/roles/Tomcat/files/Apache-tomcat-8.5.79.tar.gz
nohup command &
nohup可以使shell命令忽略SIGHUP信號，避免父進程退出時，子進程也退出。&使任務后臺執行。
[appmanager@localhost toutiao]$ nohup $HOME/tmp/toutiao/findBigFiles.bash > output.log 2>&1 &
## 退出當前終端，新開終端并查看進程
[appmanager@localhost ~]$ psfu
UID PID PPID C STIME TTY TIME CMD
appmana+ 3045 1 0 06:20 ? 00:00:00 /bin/bash /home/appmanager/tmp/toutiao/findBigFiles.bash
appmana+ 3046 3045 0 06:20 ? 00:00:00 sleep 1m
appmana+ 3102 3101 1 06:21 pts/0 00:00:00 -bash
appmana+ 3134 3102 0 06:21 pts/0 00:00:00 ps -fu appmanager
[appmanager@localhost ~]$ psfu
UID PID PPID C STIME TTY TIME CMD
appmana+ 3102 3101 0 06:21 pts/0 00:00:00 -bash
appmana+ 3154 3102 0 06:22 pts/0 00:00:00 ps -fu appmanager
[appmanager@localhost ~]$ cat tmp/toutiao/output.log
nohup: ignoring input
-rw-------. 1 appmanager devops 35M May 28 19:06 /home/appmanager/.cache/pip/http/d/6/1/f/e/d61fe4b09676f0692c240e67193e3af065d7b9e72f8577595151e51f
-rw-r--r--. 1 appmanager devops 11M May 16 08:49 /home/appmanager/mnt/ansible/roles/tomcat/files/apache-tomcat-8.5.79.tar.gz
CTRL+Z;bg %n; disown %n
使用disown可以忽略執行jobs id接收到的SIGHUP信號，避免父進程的退出而導致子進程的退出。
## CTRL + 會暫停當前執行的程序
[appmanager@localhost toutiao]$ bash -x ./findBigFiles.bash > output.log 2>&1
^Z
[1]+ Stopped bash -x ./findBigFiles.bash > output.log 2>&1
[appmanager@localhost toutiao]$ bg %1
[1]+ bash -x ./findBigFiles.bash > output.log 2>&1 &
[appmanager@localhost toutiao]$ disown %1
## 退出當前終端，新開終端并查看進程
+ sleep 1m
+ xargs ls -l --block-size=M
+ find /home/appmanager -size +10M
-rw-------. 1 appmanager devops 35M May 28 19:06 /home/appmanager/.cache/pip/http/d/6/1/f/e/d61fe4b09676f0692c240e67193e3af065d7b9e72f8577595151e51f
-rw-r--r--. 1 appmanager devops 11M May 16 08:49 /home/appmanager/mnt/ansible/roles/tomcat/files/apache-tomcat-8.5.79.tar.gz
setsid command
setsid指定當前進程的父進程為1，不受當前session的退出的影響，但是前提是需要在命令執行時就設置。
[appmanager@localhost toutiao]$ setsid ./findBigFiles.bash > output.log 2>&1 &
[1] 3823
[appmanager@localhost toutiao]$ psfu
UID PID PPID C STIME TTY TIME CMD
appmana+ 3729 3728 0 06:43 pts/0 00:00:00 -bash
appmana+ 3824 1 0 06:49 ? 00:00:00 /bin/bash ./findBigFiles.bash
appmana+ 3825 3824 0 06:49 ? 00:00:00 sleep 1m
appmana+ 3826 3729 0 06:49 pts/0 00:00:00 ps -fu appmanager
[1]+ Done setsid ./findBigFiles.bash > output.log 2>&1
## 退出當前終端，新開終端并查看進程
[appmanager@localhost toutiao]$ psfu
UID PID PPID C STIME TTY TIME CMD
appmana+ 3729 3728 0 06:43 pts/0 00:00:00 -bash
appmana+ 3824 1 0 06:49 ? 00:00:00 /bin/bash ./findBigFiles.bash
appmana+ 3825 3824 0 06:49 ? 00:00:00 sleep 1m
appmana+ 3827 3729 0 06:49 pts/0 00:00:00 ps -fu appmanager
[appmanager@localhost toutiao]$ ll
total 4
-rwx------. 1 appmanager devops 74 Jun 19 06:11 findBigFiles.bash
-rw-r--r--. 1 appmanager devops 0 Jun 19 06:49 output.log
[appmanager@localhost toutiao]$ cat /opt/
cat: /opt/: Is a directory
[appmanager@localhost toutiao]$ cat output.log
-rw-------. 1 appmanager devops 35M May 28 19:06 /home/appmanager/.cache/pip/http/d/6/1/f/e/d61fe4b09676f0692c240e67193e3af065d7b9e72f8577595151e51f
-rw-r--r--. 1 appmanager devops 11M May 16 08:49 /home/appmanager/mnt/ansible/roles/tomcat/files/apache-tomcat-8.5.79.tar.gz
