Go Cheatsheet - Run External Process

PublishedApril 23, 2021

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Run External Process

We can use os/exec module's Command function to call external program.

Use Output

proc := exec.Command("ls", "-l") output, err := proc.Output() if err != nil { log.Fatalln("Process running error", err) } fmt.Println(string(output))

Use Run

proc2 := exec.Command("cd", "/") if err := proc2.Run(); err != nil { log.Fatalln("Process running error", err) } fmt.Println(proc2.ProcessState.Success()) // true or false to indicate program successfully terminated

Use Start and Wait

Start starts the specified command but does not wait for it to complete. (Run asynchronously)

proc3 := exec.Command("ls", "-l") out := bytes.NewBuffer([]byte{}) proc3.Stdout = out proc3.Start() proc3.Wait() if proc3.ProcessState.Success() { fmt.Print(out.String()) }

Result:

total 8 -rw-r--r-- 1 johndoe staff 1237 Apr 22 23:12 main.go

Use StdoutPipe

The code below will monitor external program's stdout, and set a running max time. When the time is up, master will keep the child program.

proc4 := exec.Command("ping", "google.com") stdout, err := proc4.StdoutPipe() proc4.Start() quit := make(chan bool) ch := make(chan string) go func() { buf := make([]byte, 512) for { n, err := stdout.Read(buf) if err != nil { fmt.Println("Process stdout error", err) break } if n != 0 { ch <- string(buf[:n]) } } fmt.Println("Process ended") close(ch) }() quit := make(chan bool) time.AfterFunc(5*time.Second, func() { quit <- true }) running: for { select { case s, ok := <-ch: if !ok { break running } fmt.Print(s) case <-quit: fmt.Println("Process running timeout") proc4.Process.Kill() } }

Result:

PING google.com (172.217.9.238): 56 data bytes 64 bytes from 172.217.9.238: icmp_seq=0 ttl=116 time=13.415 ms 64 bytes from 172.217.9.238: icmp_seq=1 ttl=116 time=20.761 ms 64 bytes from 172.217.9.238: icmp_seq=2 ttl=116 time=20.706 ms 64 bytes from 172.217.9.238: icmp_seq=3 ttl=116 time=21.156 ms 64 bytes from 172.217.9.238: icmp_seq=4 ttl=116 time=19.031 ms Process running timeout Process stdout error EOF Process ended

Go Cheatsheet - Run External Process

Comments

Go Cheatsheet

Go Cheatsheet - Hmac

More from this blog

Enable cursor smooth animation in VS Code

Vue3 use v-bind in style tag

Pinia listen state change example

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Run External Process

Use `Output`

Use `Run`

Use `Start` and `Wait`

Use `StdoutPipe`

Command Palette

Comments

Go Cheatsheet

Go Cheatsheet - Hmac

More from this blog

Run External Process

Use Output

Use Run

Use Start and Wait

Use StdoutPipe

Use `Output`

Use `Run`

Use `Start` and `Wait`

Use `StdoutPipe`