[systemd-devel] [PATCH 1/2] [V3] util: add files_same() helper function

[harald at redhat.com]

From: Harald Hoyer <harald at redhat.com>

files_same() returns
     1, if the files are the same
     0, if the files have different inode/dev numbers
 errno, for any stat error
---
 src/shared/util.c | 22 +++++++++++++++-------
 src/shared/util.h |  2 ++
 2 files changed, 17 insertions(+), 7 deletions(-)

diff --git a/src/shared/util.c b/src/shared/util.c
index 588b1f5..3292854 100644
--- a/src/shared/util.c
+++ b/src/shared/util.c
@@ -3198,19 +3198,27 @@ bool on_tty(void) {
         return cached_on_tty;
 }
 
-int running_in_chroot(void) {
+int files_same(const char *filea, const char *fileb) {
         struct stat a = {}, b = {};
 
-        /* Only works as root */
-        if (stat("/proc/1/root", &a) < 0)
+        if (stat(filea, &a) < 0)
                 return -errno;
 
-        if (stat("/", &b) < 0)
+        if (stat(fileb, &b) < 0)
                 return -errno;
 
-        return
-                a.st_dev != b.st_dev ||
-                a.st_ino != b.st_ino;
+        return a.st_dev == b.st_dev && a.st_ino == b.st_ino;
+}
+
+int running_in_chroot(void) {
+        int ret;
+
+        ret = files_same("/proc/1/root", "/");
+
+        if (ret < 0)
+                return ret;
+
+        return ret == 0;
 }
 
 static char *ascii_ellipsize_mem(const char *s, size_t old_length, size_t new_length, unsigned percent) {
diff --git a/src/shared/util.h b/src/shared/util.h
index 51b1caf..c881a05 100644
--- a/src/shared/util.h
+++ b/src/shared/util.h
@@ -451,6 +451,8 @@ static inline const char *ansi_highlight_off(void) {
         return on_tty() ? ANSI_HIGHLIGHT_OFF : "";
 }
 
+int files_same(const char *filea, const char *fileb);
+
 int running_in_chroot(void);
 
 char *ellipsize(const char *s, size_t length, unsigned percent);
-- 
1.8.5.3