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  //go:build aix || darwin || dragonfly || freebsd || linux || netbsd || openbsd || solaris
     6  
     7  package exec
     8  
     9  import (
    10  	"errors"
    11  	"io/fs"
    12  	"os"
    13  	"path/filepath"
    14  	"strings"
    15  )
    16  
    17  // ErrNotFound is the error resulting if a path search failed to find an executable file.
    18  var ErrNotFound = errors.New("executable file not found in $PATH")
    19  
    20  func findExecutable(file string) error {
    21  	d, err := os.Stat(file)
    22  	if err != nil {
    23  		return err
    24  	}
    25  	if m := d.Mode(); !m.IsDir() && m&0111 != 0 {
    26  		return nil
    27  	}
    28  	return fs.ErrPermission
    29  }
    30  
    31  // LookPath searches for an executable named file in the
    32  // directories named by the PATH environment variable.
    33  // If file contains a slash, it is tried directly and the PATH is not consulted.
    34  // The result may be an absolute path or a path relative to the current directory.
    35  func LookPath(file string) (string, error) {
    36  	// NOTE(rsc): I wish we could use the Plan 9 behavior here
    37  	// (only bypass the path if file begins with / or ./ or ../)
    38  	// but that would not match all the Unix shells.
    39  
    40  	if strings.Contains(file, "/") {
    41  		err := findExecutable(file)
    42  		if err == nil {
    43  			return file, nil
    44  		}
    45  		return "", &Error{file, err}
    46  	}
    47  	path := os.Getenv("PATH")
    48  	for _, dir := range filepath.SplitList(path) {
    49  		if dir == "" {
    50  			// Unix shell semantics: path element "" means "."
    51  			dir = "."
    52  		}
    53  		path := filepath.Join(dir, file)
    54  		if err := findExecutable(path); err == nil {
    55  			return path, nil
    56  		}
    57  	}
    58  	return "", &Error{file, ErrNotFound}
    59  }
    60
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