shell for循环、循环变量值付给其他shell脚本的方法
时间：2021-06-30 09:23:04|栏目：Shell|点击： 次
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
