1 files changed, 104 insertions, 0 deletions
diff --git a/src/os/executable_path.go b/src/os/executable_path.go
new file mode 100644
index 0000000..d6161bc
--- /dev/null
+++ b/src/os/executable_path.go
@@ -0,0 +1,104 @@
+// Copyright 2017 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 aix || openbsd
+
+package os
+
+// We query the working directory at init, to use it later to search for the
+// executable file
+// errWd will be checked later, if we need to use initWd
+var initWd, errWd = Getwd()
+
+func executable() (string, error) {
+	var exePath string
+	if len(Args) == 0 || Args[0] == "" {
+		return "", ErrNotExist
+	}
+	if IsPathSeparator(Args[0][0]) {
+		// Args[0] is an absolute path, so it is the executable.
+		// Note that we only need to worry about Unix paths here.
+		exePath = Args[0]
+	} else {
+		for i := 1; i < len(Args[0]); i++ {
+			if IsPathSeparator(Args[0][i]) {
+				// Args[0] is a relative path: prepend the
+				// initial working directory.
+				if errWd != nil {
+					return "", errWd
+				}
+				exePath = initWd + string(PathSeparator) + Args[0]
+				break
+			}
+		}
+	}
+	if exePath != "" {
+		if err := isExecutable(exePath); err != nil {
+			return "", err
+		}
+		return exePath, nil
+	}
+	// Search for executable in $PATH.
+	for _, dir := range splitPathList(Getenv("PATH")) {
+		if len(dir) == 0 {
+			dir = "."
+		}
+		if !IsPathSeparator(dir[0]) {
+			if errWd != nil {
+				return "", errWd
+			}
+			dir = initWd + string(PathSeparator) + dir
+		}
+		exePath = dir + string(PathSeparator) + Args[0]
+		switch isExecutable(exePath) {
+		case nil:
+			return exePath, nil
+		case ErrPermission:
+			return "", ErrPermission
+		}
+	}
+	return "", ErrNotExist
+}
+
+// isExecutable returns an error if a given file is not an executable.
+func isExecutable(path string) error {
+	stat, err := Stat(path)
+	if err != nil {
+		return err
+	}
+	mode := stat.Mode()
+	if !mode.IsRegular() {
+		return ErrPermission
+	}
+	if (mode & 0111) == 0 {
+		return ErrPermission
+	}
+	return nil
+}
+
+// splitPathList splits a path list.
+// This is based on genSplit from strings/strings.go
+func splitPathList(pathList string) []string {
+	if pathList == "" {
+		return nil
+	}
+	n := 1
+	for i := 0; i < len(pathList); i++ {
+		if pathList[i] == PathListSeparator {
+			n++
+		}
+	}
+	start := 0
+	a := make([]string, n)
+	na := 0
+	for i := 0; i+1 <= len(pathList) && na+1 < n; i++ {
+		if pathList[i] == PathListSeparator {
+			a[na] = pathList[start:i]
+			na++
+			start = i + 1
+		}
+	}
+	a[na] = pathList[start:]
+	return a[:na+1]
+}