shell中for循环的对象如何写

目录

1、数字循环对象

（1）常量范围

（2）含有变量的范围

2、字符串循环对象

（1）常量字符串

 (2）多个字符串

（3）$*和$@区别

（4）路径循环

---

1、数字循环对象

（1）常量范围

总结4种方式：表达循环1到10

双括号： ((a=1;a<=10;a++))    遇到了awk嵌套的时候就是单括号 awk 'BEGIN{for(i=1; i<=10; i++) print i}'

大括号：{1..10}

seq反引号： `seq 1 10`

seq变量号： $(seq 1 10)

#!/bin/bash

for i in {1..10}
do
    echo -n $i
done
echo -e

for ((i=1;i<11;i++))
do
    echo -n $i
done
echo -e

for i in `seq 1 10`
do
    echo -n $i
done
echo -e

for i in $(seq 1 10)
do
    echo -n $i
done
echo -e

（2）含有变量的范围

总结3种方式：表达循环1到10

双括号：((a=1;a<=$w;a++))

seq反引号：`seq 1 $w`

seq变量号：$(seq 1 $w)

#!/bin/bash

w=10

for ((a=1;a<=$w;a++))
do
    echo -n $a
done
echo -e

for c in `seq 1 $w`
do
    echo -n $c
done
echo -e

for c in $(seq 1 $w)
do
    echo -n $c
done
echo -e

#错误的使用{}大括号目前不知道杂用，一下是错误的使用
for b in {1..$w}
do
    echo -n $b
done
echo -e

for d in {1..w}
do
    echo -n $d
done
echo -e

for b1 in `{1..$w}`
do
    echo -n $b1
done
echo -e

for b2 in $({1..$w})
do
    echo -n $b2
done

2、字符串循环对象

（1）常量字符串

总结：引号+空格切割的，引号大于空格

#!/bin/bash

for i in "data0 data1 data data2";
do
echo $i is get
done

for y in f1 f2 f3
do
echo $y is get
done

for z in "f1" "f2" "f3"
do
echo $z is get
done

  (2）字符串变量

总结：双引号加算整体，不加空格分隔

#!/bin/bash
#不加双引号怎么都是用空格分隔
list="data0 data data2"
for y in $list
do
    echo $y is get
done
echo "******************************************"

for x in ${list[*]}
do
    echo $x is get
done
echo "******************************************"

for a in ${list[@]}
do
    echo $a is get
done
echo "******************************************"

#加了双引号怎么都算整体
for y in "$list"
do
    echo $y is get
done
echo "******************************************"


for b in "${list[*]}"
do
    echo $b is get
done
echo "******************************************"

for i in "${list[@]}"
do
                              
var1="hello"
var2="world"
var3="jintian"
for z in $var1 $var2 $var3
do
echo $z is get
done

（3）$*和$@区别

区别：双引号加不加 

               $@加不加双引号没区别

               $*加双引号就是把所有入参当做整体

范围：脚本以外获取的变量

#!/bin/bash
echo "------------------不穿衣服一样------------------------"
echo $*
echo $@
for i in $*
do 
    echo $i
done

for y in $@
do 
    echo $y
done

echo "------------------穿衣服不一样------------------------"
echo $*
echo $@
for i in "$*"
do 
    echo $i
done

for y in "$@"
do 
    echo $y
done

（4）路径循环

            如何获取路径如下内容

#!/bin/bash
for file in /home/hanfang1/*;
do
echo $file is file path \! ;
done


for file in $(ls *.sh)
do
    echo $file
done

for file in `ls *.sh`
do
    echo $file
done