bash zsh awk字符串分割

fl.txt文件
12
34
56
78


Bash

1、IFS定义分隔符,默认空格、tab、换行、回车

bash-3.2$ a="a b c d"
bash-3.2$ for i in $a;
> do
> echo $i","
> done
a,
b,
c,
d,

bash-3.2$ b=`sed 'r/g' fl.txt`
bash-3.2$ for i in $b; do echo $i","; done
12,
34,
56,
78,

a="a,b,c,d"
#换行符分割
IFS=$'\n'

bash-3.2$ a="a,b,c,d"
bash-3.2$ for i in $a;
> do 
> echo $i;
> done
a,b,c,d

设置分隔符为逗号
bash-3.2$ IFS=$','
bash-3.2$ for i in $a; do  echo $i; done
a
b
c
d

2、使用分割符生成数组
bash-3.2$ aa="hello,shell,split,test"
bash-3.2$ array=(${aa//,/})
bash-3.2$ for i in ${array[@]}
> do
> echo $i
> done
Helloshellsplittest

bash-3.2$ array=(${aa/\n/,/})
bash-3.2$ for i in ${array[@]}; do echo $i; done
hello
shell
split
Test

bash-3.2$ echo ${array[0]}
hello
bash-3.2$ echo ${array[1]}
Shell


Zsh 
Zsh 不会默认使用空格、tab、换行、回车分割

1、(f)按行分割

str=$(<fl.txt)

% echo $str
12 
34 
56 
78

for i (${(f)str}){
echo $i"#"
}
12#
34# 
56# 
78#

注意，写在一起这样不行
for i (${(f)$(<fl.txt)});
do 
echo $i",";
done
12 34 56 78#

直接输出和使用变量行为不一致
echo $(<fl.txt)
12 34 56 78
aa=$(<fl.txt)
echo $aa
12
34
56
78


需要使用(s:chr:)方式
for i (${(s: :)$(<fl.txt)});
do 
echo $i",";
done


或者使用sed读取
aa=`sed 'r/g' fl.txt`;
for i (${(f)aa});
do 
echo $i",";
Done



2、(s:chr:)

s='foo,bar,baz'
#仅s也可，见过p w @，：可以用其他符号代替
for i  in ${(ps:,:)s} ; do   
echo "$i END"
done
foo END
bar END
baz END


awk

bash-3.2$ aa=`awk '{print $1}' fl.txt`
bash-3.2$ for i in $aa
> do
> echo $i
> done
12
34
56
78