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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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