Bash循环结构

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Bash循环结构

一、for结构

For arg in list Do … done

有限循环，次数取决于list元素的个数，内容取决于list元素的值

二、while结构

While […] Do … Done

条件循环，当条件为真时，执行一次循环

三、until结构

Until […] Do … done

条件循环，当条件为假时，才执行一次循环

四、case结构

Case arg in … ) … ;; … ) … ;; Esac

条件分支，注意每个分支中，条件和结果用”)”分开，结束用两个封号”;;”

五、select结构

六、代码

#! /bin/bash for item in "a" "b" "c" "d" "e" "f" do echo "$item" done #######for result #a #b #c #d #e #f a="abc def ghi jkl mno pqr" for argu in `echo $a` do echo "$argu" done ######for result #abc #def #ghi #jkl #mno #pqr b=10 c=20 while [ "$b" -lt "$c" ] do echo "b=$b" let "b=$b+1" done #######while result #b=10 #b=11 #b=12 #b=13 #b=14 #b=15 #b=16 #b=17 #b=18 #b=19 b=10 c=20 while [ "$b" -lt "$c" ] do let "b=$b+1" if [ "$b" -eq "13" ] then continue fi echo "b=$b" done #######while result #b=11 #b=12 #b=14 #b=15 #b=16 #b=17 #b=18 #b=19 #b=20 while [ "$var" != "end" ] do echo "While input variable" read var done until [ "$var" != "end" ] do echo "Until input variable" read var done echo "Hit a key, then hit return" read var case "$var" in "1" ) echo "var is 1" ;; "2" ) echo "var is 2" ;; * ) echo "var is other" ;; esac select var in "123" "456" "789" do echo "ok is $var" break done

七、关键点

1、for中的list可以用命令替换

2、read输入是var，而不是$var

3、select很直观，直接将list中的所有输出菜单样，但有待进一步。