shell for循环、循环变量值付给其他shell脚本

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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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