使用golang从命令行将输入读取到Shell脚本exec中

Question

I am using go to run a shell script using exec.command like below and I want to take an input argument using command line say i, and my output should be based on i, how would I do that?

i := os.Args[1:2]
out, err := exec.Command("bash", "-c", "tail -n 1 /var/log/apache2/access.log | awk '{print $i/1024}' >> mem_usage.csv").Output()
if err != nil {
    fmt.Println(err.Error())
    return
 }

How could I use that i in the shell script?

Without i it works fine i.e if I put $1 or $2 it works fine but I want user to give me the position of i and then calculate accordingly.

Answer 1

You need to format the exec-command string accordingly.

So ie:

fmt.Sprintf("awk '{print $%d/1024}'", i)

This gives: awk '{print $1/1024}' for i = 1 and awk '{print $2/1024}' for i = 2

fmt.Sprintf takes a format string and the arguments to pass into this string and returns the formatted string. (https://golang.org/pkg/fmt/#Sprintf)

And this needs to be inserted into your exec-command:

i := 2
awkPart := fmt.Sprintf("awk '{print $%d/1024}'", i)
out, err := exec.Command("bash", "-c", "tail -n 1 /var/log/apache2/access.log | "+awkPart+" | tee -a mem_usage.csv").Output()

You should maybe try to disassemble your command a bit more for maintainabilty, but that's not part of the question.