go.chromium.org/luci@v0.0.0-20240309015107-7cdc2e660f33/common/system/prober/probe_unix.go (about)

     1  // Copyright 2017 The LUCI Authors.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //      http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  //go:build unix
    16  // +build unix
    17  
    18  package prober
    19  
    20  import (
    21  	"os"
    22  	"path/filepath"
    23  
    24  	"go.chromium.org/luci/common/errors"
    25  	"go.chromium.org/luci/common/system/environ"
    26  )
    27  
    28  func findExecutable(file string) error {
    29  	d, err := os.Stat(file)
    30  	if err != nil {
    31  		return err
    32  	}
    33  	if m := d.Mode(); !m.IsDir() && m&0111 != 0 {
    34  		return nil
    35  	}
    36  	return os.ErrPermission
    37  }
    38  
    39  // findInDir is a paraphrased and trimmed version of "exec.LookPath"
    40  // (for Windows),
    41  //
    42  // Copied from:
    43  // https://github.com/golang/go/blob/d234f9a75413fdae7643e4be9471b4aeccf02478/src/os/exec/lp_unix.go
    44  //
    45  // Modified to:
    46  //   - Use a supplied "dir" instead of scanning through PATH.
    47  //   - Not consider cases where "file" is an absolute path
    48  //   - Ignore the possibility that "file" may be in the CWD; only look in "dir".
    49  func findInDir(file, dir string, env environ.Env) (string, error) {
    50  	// NOTE(rsc): I wish we could use the Plan 9 behavior here
    51  	// (only bypass the path if file begins with / or ./ or ../)
    52  	// but that would not match all the Unix shells.
    53  
    54  	if dir == "" {
    55  		// Unix shell semantics: path element "" means "."
    56  		dir = "."
    57  	}
    58  	path := filepath.Join(dir, file)
    59  	if err := findExecutable(path); err == nil {
    60  		return path, nil
    61  	}
    62  	return "", errors.New("not found")
    63  }