001、if
[root@centos7pc1 test]# ls test.sh [root@centos7pc1 test]# cat test.sh ## 测试脚本，if判断 #!/bin/bash read -p "please input an num:" NUM if [ $NUM -gt 0 ] then echo "you had input an positive num!" fi [root@centos7pc1 test]# bash test.sh please input an num:3 you had input an positive num! [root@centos7pc1 test]# bash test.sh please input an num:0 [root@centos7pc1 test]# bash test.sh please input an num:-8
002、if...else
[root@centos7pc1 test]# ls test.sh [root@centos7pc1 test]# cat test.sh ## 测试脚本 #!/bin/bash read -p "please input an number:" NUM if [ $NUM -gt 0 ] then echo "You had input an positive num!" else echo "You had input zero or negative num!" fi [root@centos7pc1 test]# bash test.sh please input an number:8 You had input an positive num! [root@centos7pc1 test]# bash test.sh please input an number:0 You had input zero or negative num! [root@centos7pc1 test]# bash test.sh please input an number:-8 You had input zero or negative num!
003、if...elif...else
[root@centos7pc1 test]# ls test.sh [root@centos7pc1 test]# cat test.sh ## 测试脚本 #!/bin/bash read -p "please input an number:" NUM if [ $NUM -lt 0 ] then echo " < 0 " elif [ $NUM -gt 100 ] then echo " > 100 " else echo " 0-100 " fi [root@centos7pc1 test]# bash test.sh please input an number:8 0-100 [root@centos7pc1 test]# bash test.sh please input an number:345 > 100 [root@centos7pc1 test]# bash test.sh please input an number:-325 < 0