1 files changed, 17 insertions, 0 deletions
diff --git a/src/libstddjb/fd_islocked.c b/src/libstddjb/fd_islocked.c
new file mode 100644
index 0000000..bf9f9e8
--- /dev/null
+++ b/src/libstddjb/fd_islocked.c
@@ -0,0 +1,17 @@
+/* ISC license. */
+
+#include <fcntl.h>
+
+#include <skalibs/djbunix.h>
+
+int fd_islocked (int fd)
+{
+  struct flock fl =
+  {
+    .l_type = F_RDLCK,
+    .l_whence = SEEK_SET,
+    .l_start = 0,
+    .l_len = 0
+  } ;
+  return fcntl(fd, F_GETLK, &fl) < 0 ? -1 : fl.l_type != F_UNLCK ;
+}