Source file src/pkg/os/exec/lp_unix.go

     1	// Copyright 2010 The Go Authors.  All rights reserved.
     2	// Use of this source code is governed by a BSD-style
     3	// license that can be found in the LICENSE file.
     4	
     5	// +build darwin freebsd linux netbsd openbsd
     6	
     7	package exec
     8	
     9	import (
    10		"errors"
    11		"os"
    12		"strings"
    13	)
    14	
    15	// ErrNotFound is the error resulting if a path search failed to find an executable file.
    16	var ErrNotFound = errors.New("executable file not found in $PATH")
    17	
    18	func findExecutable(file string) error {
    19		d, err := os.Stat(file)
    20		if err != nil {
    21			return err
    22		}
    23		if m := d.Mode(); !m.IsDir() && m&0111 != 0 {
    24			return nil
    25		}
    26		return os.ErrPermission
    27	}
    28	
    29	// LookPath searches for an executable binary named file
    30	// in the directories named by the PATH environment variable.
    31	// If file contains a slash, it is tried directly and the PATH is not consulted.
    32	func LookPath(file string) (string, error) {
    33		// NOTE(rsc): I wish we could use the Plan 9 behavior here
    34		// (only bypass the path if file begins with / or ./ or ../)
    35		// but that would not match all the Unix shells.
    36	
    37		if strings.Contains(file, "/") {
    38			err := findExecutable(file)
    39			if err == nil {
    40				return file, nil
    41			}
    42			return "", &Error{file, err}
    43		}
    44		pathenv := os.Getenv("PATH")
    45		for _, dir := range strings.Split(pathenv, ":") {
    46			if dir == "" {
    47				// Unix shell semantics: path element "" means "."
    48				dir = "."
    49			}
    50			path := dir + "/" + file
    51			if err := findExecutable(path); err == nil {
    52				return path, nil
    53			}
    54		}
    55		return "", &Error{file, ErrNotFound}
    56	}