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Source file src/os/exec/lp_unix.go

Documentation: os/exec

     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 named file in the
    31  // 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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