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// 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
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) {
if execerrdot.Value() != "0" {
return path, &Error{file, ErrDot}
}
execerrdot.IncNonDefault()
}
return path, nil
}
}
return "", &Error{file, ErrNotFound}
}
// lookExtensions is a no-op on non-Windows platforms, since
// they do not restrict executables to specific extensions.
func lookExtensions(path, dir string) (string, error) {
return path, nil
}
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