ironsmith/exec.go

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// Copyright 2016 Tim Shannon. All rights reserved.
// Use of this source code is governed by the MIT license
// that can be found in the LICENSE file.
package main
import (
"fmt"
"os"
"os/exec"
"path/filepath"
"strings"
)
func runCmd(cmd, dir string, env []string) ([]byte, error) {
s := strings.Fields(strings.Replace(cmd, "@dir", dir, -1))
for i := range env {
env[i] = strings.Replace(env[i], "@dir", dir, -1)
}
var args []string
if len(s) > 1 {
args = s[1:]
}
name := s[0]
ec := &exec.Cmd{
Path: name,
Args: append([]string{name}, args...),
Dir: dir,
Env: env,
}
if filepath.Base(name) == name {
lp, err := lookPath(name, env)
if err != nil {
return nil, err
}
ec.Path = lp
}
vlog("Executing command: %s in dir %s\n", cmd, dir)
result, err := ec.CombinedOutput()
if err != nil {
return nil, fmt.Errorf("%s\n%s", err, result)
}
return result, nil
}
// similar to os/exec.LookPath, except it checks if the passed in
// custom environment includes a path definitions and uses that path instead
// note this probably only works on unix, that's all I care about for now
func lookPath(file string, env []string) (string, error) {
if strings.Contains(file, "/") {
err := findExecutable(file)
if err == nil {
return file, nil
}
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return "", &exec.Error{Name: file, Err: err}
}
for i := range env {
if strings.HasPrefix(env[i], "PATH=") {
pathenv := env[i][5:]
if pathenv == "" {
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return "", &exec.Error{Name: file, Err: exec.ErrNotFound}
}
for _, dir := range strings.Split(pathenv, ":") {
if dir == "" {
// Unix shell semantics: path element "" means "."
dir = "."
}
path := dir + "/" + file
if err := findExecutable(path); err == nil {
return path, nil
}
}
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return "", &exec.Error{Name: file, Err: exec.ErrNotFound}
}
}
return exec.LookPath(file)
}
func findExecutable(file string) error {
d, err := os.Stat(file)
if err != nil {
return err
}
if m := d.Mode(); !m.IsDir() && m&0111 != 0 {
return nil
}
return os.ErrPermission
}