Shell programming (4) --- condition judgment based on if

Single branch if statement

If condition; then statement1 statement2fi

Dual-branch if statement

If judgment condition; then statement1 statement2 ...... Else statement3 statement4 ...... Fi

Multi-branch if statement

If condition 1; then statement1 statement2 ...... Elif judgment condition 2; then statement3 statement4 ...... Elif judgment Condition 3; then statement5 statement6 ...... Else statement7 statement8 ...... Fi

Example 1:

[[email protected] Scripts]# cat ./root.sh#!/bin/bashread -p "Please input an Username in /etc/passwd file: " Local_USERLocal_ID=$(id -u $Local_USER)if [ "$Local_ID" -eq 0 ];then        echo "The User $Local_USER is admin"else        echo "The User $Local_USER is common user."fi[[email protected] Scripts]# ./root.sh Please input an Username in /etc/passwd file: frameThe User frame is common user.[[email protected] Scripts]# ./root.sh Please input an Username in /etc/passwd file: rootThe User root is admin[[email protected] Scripts]#

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