lp_plan9.go

     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  // On success, the result is an absolute path.
    34  //
    35  // In older versions of Go, LookPath could return a path relative to the current directory.
    36  // As of Go 1.19, LookPath will instead return that path along with an error satisfying
    37  // [errors.Is](err, [ErrDot]). See the package documentation for more details.
    38  func LookPath(file string) (string, error) {
    39  	// skip the path lookup for these prefixes
    40  	skip := []string{"/", "#", "./", "../"}
    41  
    42  	for _, p := range skip {
    43  		if strings.HasPrefix(file, p) {
    44  			err := findExecutable(file)
    45  			if err == nil {
    46  				return file, nil
    47  			}
    48  			return "", &Error{file, err}
    49  		}
    50  	}
    51  
    52  	path := os.Getenv("path")
    53  	for _, dir := range filepath.SplitList(path) {
    54  		path := filepath.Join(dir, file)
    55  		if err := findExecutable(path); err == nil {
    56  			if !filepath.IsAbs(path) {
    57  				if execerrdot.Value() != "0" {
    58  					return path, &Error{file, ErrDot}
    59  				}
    60  				execerrdot.IncNonDefault()
    61  			}
    62  			return path, nil
    63  		}
    64  	}
    65  	return "", &Error{file, ErrNotFound}
    66  }
    67  
    68  // lookExtensions is a no-op on non-Windows platforms, since
    69  // they do not restrict executables to specific extensions.
    70  func lookExtensions(path, dir string) (string, error) {
    71  	return path, nil
    72  }
    73
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