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Source file src/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 dragonfly freebsd linux nacl netbsd openbsd solaris
     6	
     7	package exec
     8	
     9	import (
    10		"errors"
    11		"os"
    12		"path/filepath"
    13		"strings"
    14	)
    15	
    16	// ErrNotFound is the error resulting if a path search failed to find an executable file.
    17	var ErrNotFound = errors.New("executable file not found in $PATH")
    18	
    19	func findExecutable(file string) error {
    20		d, err := os.Stat(file)
    21		if err != nil {
    22			return err
    23		}
    24		if m := d.Mode(); !m.IsDir() && m&0111 != 0 {
    25			return nil
    26		}
    27		return os.ErrPermission
    28	}
    29	
    30	// LookPath searches for an executable binary named file
    31	// in the directories named by the PATH environment variable.
    32	// If file contains a slash, it is tried directly and the PATH is not consulted.
    33	// The result may be an absolute path or a path relative to the current directory.
    34	func LookPath(file string) (string, error) {
    35		// NOTE(rsc): I wish we could use the Plan 9 behavior here
    36		// (only bypass the path if file begins with / or ./ or ../)
    37		// but that would not match all the Unix shells.
    38	
    39		if strings.Contains(file, "/") {
    40			err := findExecutable(file)
    41			if err == nil {
    42				return file, nil
    43			}
    44			return "", &Error{file, err}
    45		}
    46		path := os.Getenv("PATH")
    47		for _, dir := range filepath.SplitList(path) {
    48			if dir == "" {
    49				// Unix shell semantics: path element "" means "."
    50				dir = "."
    51			}
    52			path := filepath.Join(dir, file)
    53			if err := findExecutable(path); err == nil {
    54				return path, nil
    55			}
    56		}
    57		return "", &Error{file, ErrNotFound}
    58	}
    59	

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