subprocess/path.go

// Copyright 2010 The Go Authors. All rights reserved.
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package subprocess

import (
	"os"
	"os/exec"
	"path/filepath"
	"runtime"
	"strings"
)

// LookPath searches for an executable named file in the
// directories named by the PATH environment variable.
// If file contains a slash, it is tried directly and the PATH is not consulted.
// The result may be an absolute path or a path relative to the current directory.
func LookPath(file string) (string, error) {
	sep := string([]rune{os.PathSeparator})
	exts := findPathExtensions()
	if strings.Contains(file, sep) {
		path, err := findExecutable(file, exts)
		if err == nil {
			return path, nil
		}
		return "", exec.ErrNotFound
	}
	path := os.Getenv("PATH")
	for _, dir := range filepath.SplitList(path) {
		if dir == "" {
			// Windows often has empty components in the PATH and
			// treating them as "." is not expected.
			if runtime.GOOS == "windows" {
				continue
			}
			// Unix shell semantics: path element "" means "."
			dir = "."
		}
		path := filepath.Join(dir, file)
		if resolved, err := findExecutable(path, exts); err == nil {
			return resolved, nil
		}
	}
	return "", exec.ErrNotFound
}