Shell Scripting Exercise 1

#!/bin/Bash while : DoRead-P">>>"user [["$user"="Q"]] || [["$user"="Q"]] &&Break [[-Z $user]] &&ContinueID$user &>/dev/NULL    [[ $? -eq0]] &&Cat/etc/passwd|awk-F:'{print $, $NF}'|grep$user | |Echo "User not exist" Done

The script implements the target to determine whether the user exists

Main ideas

The while do statement implements the loop

Add variable $user exit mechanism use "| |", "&&", respectively, with operations and or operations, to loop out.

[[-Z $user]] determine if $user is null continue jumps into the next loop

$? The exit state of the last command, or the return value of the function

Determines whether the print profile is in the row ($NF to the last field) as a null value

By the way, recall the comparison size parameters in the shell script

-eq//equals

-ne//Not equal to

-GT//greater than

-LT//Less than

-ge//greater than or equal

-le//less than or equal to

Shell Scripting Exercise 1