2 files changed, 13 insertions, 0 deletions
diff --git a/src/libutil/util.cc b/src/libutil/util.cc
index b1231e45574f..dad5f624bd00 100644
--- a/src/libutil/util.cc
+++ b/src/libutil/util.cc
@@ -148,6 +148,15 @@ string baseNameOf(const Path & path)
 }
 
 
+bool isInDir(const Path & path, const Path & dir)
+{
+    return path[0] == '/'
+        && string(path, 0, dir.size()) == dir
+        && path.size() >= dir.size() + 2
+        && path[dir.size()] == '/';
+}
+
+
 struct stat lstat(const Path & path)
 {
     struct stat st;
diff --git a/src/libutil/util.hh b/src/libutil/util.hh
index 9caab4aa1067..6c83987c5d46 100644
--- a/src/libutil/util.hh
+++ b/src/libutil/util.hh
@@ -45,6 +45,10 @@ Path dirOf(const Path & path);
    following the final `/'. */
 string baseNameOf(const Path & path);
 
+/* Check whether a given path is a descendant of the given
+   directory. */
+bool isInDir(const Path & path, const Path & dir);
+
 /* Get status of `path'. */
 struct stat lstat(const Path & path);