shell for循环、循环变量值付给其他shell脚本

比眉伴天荒 2022-06-14 11:53 257阅读 0赞

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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