| // Copyright 2010 The Go Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style |
| // license that can be found in the LICENSE file. |
| |
| //go:build unix || fuchsia |
| |
| package exec |
| |
| import ( |
| "errors" |
| "internal/syscall/unix" |
| "io/fs" |
| "os" |
| "path/filepath" |
| "strings" |
| "syscall" |
| ) |
| |
| // ErrNotFound is the error resulting if a path search failed to find an executable file. |
| var ErrNotFound = errors.New("executable file not found in $PATH") |
| |
| func findExecutable(file string) error { |
| d, err := os.Stat(file) |
| if err != nil { |
| return err |
| } |
| m := d.Mode() |
| if m.IsDir() { |
| return syscall.EISDIR |
| } |
| err = unix.Eaccess(file, unix.X_OK) |
| // ENOSYS means Eaccess is not available or not implemented. |
| // EPERM can be returned by Linux containers employing seccomp. |
| // In both cases, fall back to checking the permission bits. |
| if err == nil || (err != syscall.ENOSYS && err != syscall.EPERM) { |
| return err |
| } |
| if m&0111 != 0 { |
| return nil |
| } |
| return fs.ErrPermission |
| } |
| |
| // LookPath searches for an executable named file in the |
| // directories named by the PATH environment variable. |
| // If file contains a slash, it is tried directly and the PATH is not consulted. |
| // Otherwise, on success, the result is an absolute path. |
| // |
| // In older versions of Go, LookPath could return a path relative to the current directory. |
| // As of Go 1.19, LookPath will instead return that path along with an error satisfying |
| // errors.Is(err, ErrDot). See the package documentation for more details. |
| func LookPath(file string) (string, error) { |
| // NOTE(rsc): I wish we could use the Plan 9 behavior here |
| // (only bypass the path if file begins with / or ./ or ../) |
| // but that would not match all the Unix shells. |
| |
| if strings.Contains(file, "/") { |
| err := findExecutable(file) |
| if err == nil { |
| return file, nil |
| } |
| return "", &Error{file, err} |
| } |
| path := os.Getenv("PATH") |
| for _, dir := range filepath.SplitList(path) { |
| if dir == "" { |
| // Unix shell semantics: path element "" means "." |
| dir = "." |
| } |
| path := filepath.Join(dir, file) |
| if err := findExecutable(path); err == nil { |
| if !filepath.IsAbs(path) && execerrdot.Value() != "0" { |
| return path, &Error{file, ErrDot} |
| } |
| return path, nil |
| } |
| } |
| return "", &Error{file, ErrNotFound} |
| } |