golang exec.Command错误no such file or directory

拼搏现实的明天。 2022-02-26 10:42 485阅读 0赞

### 问题 ###

执行

out, err := exec.Command("grep 172.0.0.1 ~/.ssh/known_hosts | wc -l").Output()

返回RT错误

### 原因 ###

exec包

func Command(name string, arg ...string) *Cmd

name参数一定要注意

> If name contains no path separators, Command uses LookPath to resolve name to a complete path if possible. Otherwise it uses name directly as Path.

name不要写整条命令！！！  
name不要写整条命令！！！  
name不要写整条命令！！！

重要的事情说三遍

### 解决办法 ###

第一个name参数是命令的名字或路径，参数一定要挨个传入

out, err := exec.Command("grep", "172.0.0.1",  "~/.ssh/known_hosts").Output()
    out, err = exec.Command("wc", "-l",  "~/.ssh/known_hosts").Output()

如果是多命令，写成脚本 [grep.sh][]

out, err := exec.Command("sh", "grep.sh").Output()

### golang官宣 ###

> Command returns the Cmd struct to execute the named program with the given arguments.
> 
> It sets only the Path and Args in the returned structure.
> 
> If name contains no path separators, Command uses LookPath to resolve name to a complete path if possible. Otherwise it uses name directly as Path.
> 
> The returned Cmd’s Args field is constructed from the command name followed by the elements of arg, so arg should not include the command name itself. For example, Command(“echo”, “hello”). Args\[0\] is always name, not the possibly resolved Path.
> 
> On Windows, processes receive the whole command line as a single string and do their own parsing. Command combines and quotes Args into a command line string with an algorithm compatible with applications using CommandLineToArgvW (which is the most common way). Notable exceptions are msiexec.exe and cmd.exe (and thus, all batch files), which have a different unquoting algorithm. In these or other similar cases, you can do the quoting yourself and provide the full command line in SysProcAttr.CmdLine, leaving Args empty.

package main
    
    import (
    	"bytes"
    	"fmt"
    	"log"
    	"os/exec"
    	"strings"
    )
    
    func main() { 
    	cmd := exec.Command("tr", "a-z", "A-Z")
    	cmd.Stdin = strings.NewReader("some input")
    	var out bytes.Buffer
    	cmd.Stdout = &out
    	err := cmd.Run()
    	if err != nil { 
    		log.Fatal(err)
    	}
    	fmt.Printf("in all caps: %q\n", out.String())
    }

package main
    
    import (
    	"log"
    	"os"
    	"os/exec"
    )
    
    func main() { 
    	cmd := exec.Command("prog")
    	cmd.Env = append(os.Environ(),
    		"FOO=duplicate_value", // ignored
    		"FOO=actual_value",    // this value is used
    	)
    	if err := cmd.Run(); err != nil { 
    		log.Fatal(err)
    	}
    }

参考  
[https://golang.org/pkg/os/exec/\#Command][https_golang.org_pkg_os_exec_Command]

[grep.sh]: http://grep.sh
[https_golang.org_pkg_os_exec_Command]: https://golang.org/pkg/os/exec/#Command