1 files changed, 99 insertions, 0 deletions
diff --git a/walk.c b/walk.c
new file mode 100644
index 0000000..6cce89a
--- /dev/null
+++ b/walk.c
@@ -0,0 +1,99 @@
+// Copyright 2019 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <dirent.h>
+
+static const char *const JUST_CURRENT_DIRECTORY[] = {".", NULL};
+
+// Like readdir(3), but resets errno(3) before the call to make it easy to
+// check.
+static struct dirent *readdir2(DIR *const dirp)
+{
+	errno = 0;
+	return readdir(dirp);
+}
+
+// Like realloc(3), but exits the binary in an out-of-memory situation.
+static void *realloc2(void *ptr, const size_t size)
+{
+	if (!(ptr = realloc(ptr, size))) {
+		perror("realloc");
+		exit(EXIT_FAILURE);
+	}
+	return ptr;
+}
+
+static void strcpy3(char *dest, const char *s1, const char *s2, const char *s3)
+{
+	stpcpy(stpcpy(stpcpy(dest, s1), s2), s3);
+}
+
+// Walks the directory named dirname, printing the names of all files it
+// contains (but not the name of the directory itself). Returns 2 if dirname is
+// not a directory and 1 if another error occurs.
+static int walk(const char dirname[])
+{
+	DIR *const dir = opendir(dirname);
+	if (!dir) {
+		if (errno != ENOTDIR) {
+			perror(dirname);
+			return 1;
+		}
+		return 2;
+	}
+	int r = 0;
+	char *filename = NULL;
+	for (const struct dirent *f = readdir2(dir); f; f = readdir2(dir)) {
+		if (strcmp(f->d_name, ".") == 0
+				|| strcmp(f->d_name, "..") == 0)
+			continue;
+		filename = realloc2(filename,
+			strlen(dirname) + 1 + strlen(f->d_name) + 1);
+		strcpy3(filename, dirname, "/", f->d_name);
+		// TODO(bbaren): Emulate Plan 9's cleanname(3).
+		puts(filename);
+		// Walk the file if we can successfully open it as a directory.
+		// Don't worry about it if it's not one (walk(filename) == 2).
+		if ((f->d_type == DT_DIR || f->d_type == DT_UNKNOWN)
+				&& walk(filename) == 1)
+			r = 1;
+	}
+	if (errno) {	// from readdir
+		perror(dirname);
+		r = 1;
+	}
+	free(filename);
+	if (closedir(dir)) {
+		perror(dirname);
+		r = 1;
+	}
+	return r;
+}
+
+int main(const int argc, const char *const argv[])
+{
+	int r = 0;
+	const char *const *const dirs =
+		argc == 1 ? JUST_CURRENT_DIRECTORY : argv + 1;
+	for (int i = 0; dirs[i]; ++i) {
+		puts(dirs[i]);
+		r |= walk(dirs[i]);
+	}
+	return r;
+}