diff --git a/doc/byte_str.3.md b/doc/byte_str.3.md
new file mode 100644
index 0000000..2a780eb
--- /dev/null
+++ b/doc/byte_str.3.md
@@ -0,0 +1,27 @@
+% limb manual
+% byte_str(3)
+
+# NAME
+
+byte\_str - locate a substring within a string
+
+# SYNOPSIS
+
+    #include <limb/bytestr.h>
+
+```pre hl
+size_t byte_str(const char *<em>haystack</em>, size_t <em>hlen</em>, const char *<em>needle</em>, size_t <em>nlen</em>)
+```
+
+# DESCRIPTION
+
+The `byte_str`() function looks for the first occurrence of the byte array
+`needle` of length `nlen` in the byte array `haystack` of length `hlen`.
+
+Neither `haystack` nor `needle` need be NUL-terminated, and in fact can contain
+themselves bytes of any value.
+
+# RETURN VALUE
+
+The `byte_str`() function returns the offset of the first occurrence of `needle`
+within `haystack` if found. Otherwise, it returns `hlen`.
diff --git a/doc/bytestr.h.0.md b/doc/bytestr.h.0.md
new file mode 100644
index 0000000..ddb7b2f
--- /dev/null
+++ b/doc/bytestr.h.0.md
@@ -0,0 +1,25 @@
+% limb manual
+% bytestr.h(0)
+
+# NAME
+
+bytestr.h - byte arrays/strings functions
+
+# SYNOPSIS
+
+    #include <limb/bytestr.h>
+
+# DESCRIPTION
+
+This header defines functions to work with byte arrays and/or strings.
+
+! INFO: skalibs
+! This header is a complement to skalibs' own [skalibs/bytestr.h](0) and thusly
+! includes said header.
+
+## Functions
+
+The following functions are defined :
+
+: [byte_str](3)
+:: To locate a substring within a string
diff --git a/include/limb/bytestr.h b/include/limb/bytestr.h
new file mode 100644
index 0000000..3ab983b
--- /dev/null
+++ b/include/limb/bytestr.h
@@ -0,0 +1,11 @@
+/* This file is part of limb                           https://lila.oss/limb
+ * Copyright (C) 2023 Olivier Brunel                          jjk@jjacky.com */
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef LIMB_BYTESTR_H
+#define LIMB_BYTESTR_H
+
+#include <skalibs/bytestr.h>
+
+extern size_t byte_str(const char *haystack, size_t hlen, const char *needle, size_t nlen);
+
+#endif /* LIMB_BYTESTR_H */
diff --git a/meta/libs/limb b/meta/libs/limb
index 33e34cc..ec05868 100644
--- a/meta/libs/limb
+++ b/meta/libs/limb
@@ -20,6 +20,8 @@ obj/sareadlinkat0.o
 obj/sacoloff.o
 obj/saoff2ptr.o
 obj/sacolptr.o
+# bytestr.h
+obj/byte_str.o
 # buffer.h
 obj/buffer_putescall.o
 obj/buffer_putesc.o
diff --git a/src/byte_str.c b/src/byte_str.c
new file mode 100644
index 0000000..cb495aa
--- /dev/null
+++ b/src/byte_str.c
@@ -0,0 +1,12 @@
+/* This file is part of limb                           https://lila.oss/limb
+ * Copyright (C) 2023 Olivier Brunel                          jjk@jjacky.com */
+/* SPDX-License-Identifier: GPL-2.0-only */
+#include <skalibs/posixplz.h>
+#include "limb/bytestr.h"
+
+size_t
+byte_str(const char *haystack, size_t hlen, const char *needle, size_t nlen)
+{
+    char *s = memmem(haystack, hlen, needle, nlen);
+    return (s) ? s - haystack : hlen;
+}