Basic usage of shell script

Combined with daily use scenarios , Keep adding ~

1、 Stop the method immediately when there is a problem

set Ordered -e Parameters ,linux The description of the system is ："Exit immediately if a simple command exits with a non-zero status.", in other words , stay "set -e" Then the code appears , Once the return value is non-zero , The entire script will exit immediately , Then you can avoid some dangerous operations of scripts .

  Let's look at two examples of comparison , It's easy to understand , Suppose the file name is demo.sh.

Example 1： Yes set -e

#!/bin/sh

set -e
ls /not_exist_dir/leo
echo $?
ls

Output is as follows , You can see that the program exits the first time you encounter an error , because /not_exist_dir/leo file does not exist , The error code returned at this time is not 0

$ sh demo.sh
ls: cannot access /not_exist_dir/leo: No such file or directory

Example 2： No, set -e

#!/bin/sh

# set -e
ls /not_exist_dir/leo
echo $?
ls

Output is as follows , You can see that all the orders are executed this time ,"ls /not_exist_dir/leo" The error code after executing the command is 2, But it did not hinder the implementation of the program .

ls: cannot access /not_exist_dir/leo: No such file or directory
2
AGILE_OUT
demo.sh

in addition , Directly returning the exit code can be used exit command , such as ：

demo.sh

if [[ "$1" == "1" ]];then
	echo 'your input is 1,OK'
	exit 0
else
	echo 'your input is not 1,not OK'
	exit 1
fi

  test ：

【1】 scene 1
$ sh demo.sh 2
your input is not 1,not OK

$ echo $?
1


【2】 scene 2
$ sh demo.sh 1
your input is 1,OK

$ echo $?
0