linux shell for 循环变量 shell for循环 循环变量值付给其他shell脚本的方法

本文主要将在shell中如何编写for循环，并将循环变量作为下个shell脚本的参数。

shell for 循环：

#!第一种写法 类似c、java

for ((i=1; i<=100; i ++))

do

echo $i

done

#!第二种写法 in应用

for i in {1..100}

do

echo $i

done

#!第三种写法 seq 使用

for i in `seq 1 100`

do

echo $i

done

将循环变量赋值到下一个脚本：

在运行shell脚本时候，有三种方式来调用外部的脚本，exec(exec script.sh)、source(source script.sh)、fork(./script.sh)

1、exec(exec /home/script.sh)：

使用exec来调用脚本，被执行的脚本会继承当前shell的环境变量。但事实上exec产生了新的进程，他会把主shell的进程资源占用并替换脚本内容，继承了原主shell的pid号，即原主shell剩下的内容不会执行。

2、source(source /home/script.sh)

使用source或者“.”来调用外部脚本，不会产生新的进程，继承当前shell环境变量，而且被调用的脚本运行结束后，它拥有的环境变量和声明变量会被当前shell保留，类似将调用脚本的内容复制过来直接执行。执行完毕后原主shell继续运行。

3、fork(/home/script.sh)

直接运行脚本，会以当前shell为父进程，产生新的进程，并且继承主脚本的环境变量和声明变量。执行完毕后，主脚本不会保留其环境变量和声明变量。

#!main.sh主体

#!/bin/sh

a=main

echo "a is $a"

echo "pid for parent before 2.sh:$$"

case $1 in

exec)

echo "using exec"

exec ./2.sh ;;

*)

echo "using sourcing"

source ./2.sh ;;

esac

echo "pid for parent after 2.sh :$$"

echo "now m"

#！2.sh

#!/bin/sh

echo "pid for 2.sh:$$"

echo "2.sh get a from main.sh is $a"

a=2.sh

export a

b=3.sh

echo "now 2.sh a is $a"

执行结果：

a is main

pid for parent before 2.sh:1162

using sourcing

pid for 2.sh:1162

2.sh get a from main.sh is main`这里写代码片`

now 2.sh a is 2.sh

pid for parent after 2.sh :1162

now m

通过for循环，循环变量作为2.sh变量赋值并执行。

#！main主函数

#!/bin/sh

a=0

for ((i=1; i<=10; i ++))

do

a=$i

echo "a is $a"

echo "pid for parent before 2.sh:$$"

echo "using sourcing"

source ./2.sh

echo "pid for parent after 2.sh :$$"

echo "now a is $a"

done

输出结果：

a is 1

pid for parent before 2.sh:1339

using sourcing

pid for 2.sh:1339

2.sh get a from main.sh is 1

now 2.sh a is 2.sh

pid for parent after 2.sh :1339

now a is 2.sh

a is 2

pid for parent before 2.sh:1339

using sourcing

pid for 2.sh:1339

2.sh get a from main.sh is 2

now 2.sh a is 2.sh

pid for parent after 2.sh :1339

now a is 2.sh

a is 3

pid for parent before 2.sh:1339

using sourcing

pid for 2.sh:1339

2.sh get a from main.sh is 3

now 2.sh a is 2.sh

pid for parent after 2.sh :1339

now a is 2.sh

a is 4

pid for parent before 2.sh:1339

using sourcing

pid for 2.sh:1339

2.sh get a from main.sh is 4

now 2.sh a is 2.sh

pid for parent after 2.sh :1339

now a is 2.sh

a is 5

pid for parent before 2.sh:1339

using sourcing

pid for 2.sh:1339

2.sh get a from main.sh is 5

now 2.sh a is 2.sh

pid for parent after 2.sh :1339

now a is 2.sh

a is 6

pid for parent before 2.sh:1339

using sourcing

pid for 2.sh:1339

2.sh get a from main.sh is 6

now 2.sh a is 2.sh

pid for parent after 2.sh :1339

now a is 2.sh

a is 7

pid for parent before 2.sh:1339

using sourcing

pid for 2.sh:1339

2.sh get a from main.sh is 7

now 2.sh a is 2.sh

pid for parent after 2.sh :1339

now a is 2.sh

a is 8

pid for parent before 2.sh:1339

using sourcing

pid for 2.sh:1339

2.sh get a from main.sh is 8

now 2.sh a is 2.sh

pid for parent after 2.sh :1339

now a is 2.sh

a is 9

pid for parent before 2.sh:1339

using sourcing

pid for 2.sh:1339

2.sh get a from main.sh is 9

now 2.sh a is 2.sh

pid for parent after 2.sh :1339

now a is 2.sh

a is 10

pid for parent before 2.sh:1339

using sourcing

pid for 2.sh:1339

2.sh get a from main.sh is 10

now 2.sh a is 2.sh

pid for parent after 2.sh :1339

now a is 2.sh

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