Shell script Programming selection execution if statement

Single-branch if statement:

if test condition

Then

Code Branch

Fi

Two-branch if statement:

if test condition; Then

Branch that is executed when the condition is true

Else

Branch that is executed when the condition is false

Fi

Example: Pass a user name to the script through a parameter, add it when this user is not saved;

#!/bin/bash#if [$#-lt 1];    Then echo "At least one username." Exit 2fiif grep "^$1\>"/etc/passwd &>/dev/null; Then echo "User $ exists." Else Useradd echo $ | passwd--stdin $ &>/dev/null echo "ADD user $ finished." Fi

Exercise 1: Given two numbers by command-line arguments, output a larger number;

#!/bin/bash#if [$#-lt 2];    Then echo "the integers." Exit 2fiif [$1-ge]; Then echo "Max Number: $." else echo "Max number: $." Fiecho "Max number: $max."

This article is from the "Wang Liming" blog, make sure to keep this source http://afterdawn.blog.51cto.com/7503144/1915972

Shell script Programming selection execution if statement