最新消息:20190717 VPS服务器:Vultr新加坡,WordPress主题:大前端D8,统一介绍入口:关于

Exit Status in Linux

Linux crifan 688浏览 0评论

Exit Status

By default in Linux if particular command/shell script is executed, it return two type of values which is used to see whether command or shell script executed is successful or not.

(1) If return value is zero (0), command is successful.
(2) If return value is nonzero, command is not successful or some sort of error executing command/shell script.

This value is know as Exit Status.

But how to find out exit status of command or shell script?
Simple, to determine this exit Status you can use $? special variable of shell.

For e.g. (This example assumes that unknow1file doest not exist on your hard drive)
$ rm unknow1file
It will show error as follows
rm: cannot remove `unkowm1file’: No such file or directory
and after that if you give command
$ echo $?
it will print nonzero value to indicate error. Now give command
$ ls
$ echo $?

It will print 0 to indicate command is successful.

Exercise
Try the following commands and not down the exit status:
$ expr 1 + 3
$ echo $?


$ echo Welcome
$ echo $?

$ wildwest canwork?
$ echo $?

$ date
$ echo $?

$ echon $?
$ echo $?

Shell Built in Variables

Shell Built in VariablesMeaning
$#Number of command line arguments. Useful to test no. of command line args in shell script.
$*All arguments to shell
$@Same as above
$-Option supplied to shell
$$PID of shell
$!PID of last started background process (started with &)

转载请注明:在路上 » Exit Status in Linux

发表我的评论
取消评论

表情

Hi,您需要填写昵称和邮箱!

  • 昵称 (必填)
  • 邮箱 (必填)
  • 网址
55 queries in 0.219 seconds, using 18.86MB memory