github.com/code-reading/golang@v0.0.0-20220303082512-ba5bc0e589a3/go/src/os/exec/lp_plan9.go (about)

     1  // Copyright 2011 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  package exec
     6  
     7  import (
     8  	"errors"
     9  	"io/fs"
    10  	"os"
    11  	"path/filepath"
    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 fs.ErrPermission
    27  }
    28  
    29  // LookPath searches for an executable named file in the
    30  // directories named by the path environment variable.
    31  // If file begins with "/", "#", "./", or "../", it is tried
    32  // 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  	// skip the path lookup for these prefixes
    36  	skip := []string{"/", "#", "./", "../"}
    37  
    38  	for _, p := range skip {
    39  		if strings.HasPrefix(file, p) {
    40  			err := findExecutable(file)
    41  			if err == nil {
    42  				return file, nil
    43  			}
    44  			return "", &Error{file, err}
    45  		}
    46  	}
    47  
    48  	path := os.Getenv("path")
    49  	for _, dir := range filepath.SplitList(path) {
    50  		path := filepath.Join(dir, file)
    51  		if err := findExecutable(path); err == nil {
    52  			return path, nil
    53  		}
    54  	}
    55  	return "", &Error{file, ErrNotFound}
    56  }