Go exec.Command

The Command returns the Cmd struct to execute the specified program with the given arguments. The first parameter is the program to be run; the other arguments are parameters to the program.

Example of Go Exec.Command

package main

import (
    "bytes"
    "fmt"
    "log"
    "os/exec"
    "strings"
)

func main() {
    cmd := exec.Command("tr", "a-z", "A-Z")

    cmd.Stdin = strings.NewReader("and old falcon")

    var out bytes.Buffer
    cmd.Stdout = &out

    err := cmd.Run()

    if err != nil {
        log.Fatal(err)
    }

    fmt.Printf("translated phrase: %q\n", out.String())
}

In the example, we transform the input via the tr command.

cmd := exec.Command("tr", "a-z", "A-Z")

The tr standard Linux command translates, squeezes, and/or deletes characters from standard input, writing to standard output. In our case, we transform lowercase letters to uppercase ones.

cmd.Stdin = strings.NewReader("and old falcon")

Through the Stdin field, we pass a string to the command as its input.

var out bytes.Buffer
cmd.Stdout = &out

The output of the program will be written to the bytes buffer.

$ go run command.go 
translated phrase: "AND OLD FALCON"

Go exec command with multiple args

We can pass multiple arguments to the exec.Command.

package main

import (
    "fmt"
    "os/exec"
)

func main() {

    prg := "echo"

    arg1 := "there"
    arg2 := "are three"
    arg3 := "falcons"

    cmd := exec.Command(prg, arg1, arg2, arg3)
    stdout, err := cmd.Output()

    if err != nil {
        fmt.Println(err.Error())
        return
    }

    fmt.Print(string(stdout))
}

The example runs the echo command with three arguments.

$ go run multiple_args.go 
there are three falcons

Go exec command capture output

The Output runs the command and returns its standard output.

package main

import (
    "fmt"
    "log"
    "os/exec"
)

func main() {

    out, err := exec.Command("ls", "-l").Output()

    if err != nil {
        log.Fatal(err)
    }

    fmt.Println(string(out))
}

The example captures the output of the ls command and prints it.

Conclusion

In this page (written and validated by A. Gawali) you learned about Go Exec Command . What's Next? If you are interested in completing Go tutorial, your next topic will be learning about: Go Pointers.

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