如何在shell文件中使用awk的$ 0变量

Question

1.my shell file is

 [root@node3 script]# cat hi.sh
 #!/bin/bash
 strings="sdsf sdsda sdsadx"
 echo `awk "{print substr($0,0,9)}"<<<$strings`

2.exe my shell file

[root@node3 script]# sh hi.sh 

awk: {print substr(hi.sh,0,9)}

awk:                 ^ syntax error

awk: 致命错误: 0 是 substr 的无效参数个数

so how to use the awk's $0 in shell file ?

the $0 default file's name .

another ques. i want use the var $0 about awk but the another $variable in the shell file.what should i do ?

$ cat hi.sh 
#!/bin/bash 
strings="sdsf sdsda sdsadx" 
num=9 
echo \`awk '{print substr($0,0,$num)}' <<< $strings\`

Answer 1

The problem with your script is use of double quotes in awk. Replace them with single quotes.

When you use double quotes, the $0 inside it is treated as first argument to the script, which in this case is script name hi.sh . If you use single quotes, you can use $0 as awk argument to display whole row.

Also echo is not needed here, you can just use awk '{print substr($0,0,9)}' <<< $strings

$ cat hi.sh
#!/bin/bash
strings="sdsf sdsda sdsadx"
#echo `awk '{print substr($0,0,9)}' <<< $strings` --echo not needed
awk '{print substr($0,0,9)}' <<< $strings
$
$ sh hi.sh
sdsf sdsd