diff --git a/lib/cstr.c b/lib/cstr.c
new file mode 100644
index 0000000..8dd024b
--- /dev/null
+++ b/lib/cstr.c
@@ -0,0 +1,62 @@
+#include "cstr.h"
+#include <ctype.h>
+#include <string.h>
+
+/**
+ * trim whitespace of a cstring (both beginning and end). a null terminator
+ * will be placed after the last non-whitespace character. this modifies the
+ * string.
+ *
+ * @param   str: the string to trim
+ *
+ * @return  a pointer to the beginning of the trimmed string. the string is not
+ *          copied, and the returned pointer points to somewhere within the
+ *          original string.
+ */
+char *
+strtrim (char *str)
+{
+    strtrimr (str);
+    return strtriml (str);
+}
+
+/**
+ * trim whitespace of a cstring on the left (beginning of string). the original
+ * string will be preserved.
+ *
+ * @param   str: the string to trim
+ *
+ * @return  a pointer to the beginning of the trimmed string. the string is not
+ *          copied, and the returned pointer points to somewhere within the
+ *          original string.
+ */
+char *
+strtriml (const char *str)
+{
+    while (*str && isspace (*str))
+        str++;
+
+    return str;
+}
+
+/**
+ * trim whitespace of a cstring on the right (end of string). a null terminator
+ * will be placed after the last non-whitespace character. this modifies the
+ * string.
+ *
+ * @param   str: the string to trim
+ *
+ * @return  the new string length
+ */
+size_t
+strtrimr (char *str)
+{
+    size_t len, i;
+
+    i = len = strlen (str);
+    while (i <= len && isspace (str[i - 1]))
+        i--;
+    str[i] = '\0';
+
+    return i;
+}
diff --git a/lib/inc/cstr.h b/lib/inc/cstr.h
new file mode 100644
index 0000000..f4f9639
--- /dev/null
+++ b/lib/inc/cstr.h
@@ -0,0 +1,10 @@
+#ifndef CUTILS_CSTR_H_
+#define CUTILS_CSTR_H_
+
+#include <stddef.h>
+
+char *strtrim (char *str); /* trim whitespace of a cstring (both beginning and end) */
+char *strtriml (const char *str); /* trim whitespace of a cstring on the left (beginning of string). */
+size_t strtrimr (char *str); /* trim whitespace of a cstring on the right (end of string) */
+
+#endif // CUTILS_CSTR_H_
diff --git a/test/main.c b/test/main.c
index 2b210c5..09da880 100644
--- a/test/main.c
+++ b/test/main.c
@@ -1,6 +1,9 @@
+#include <assert.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 
+#include "cstr.h"
 #define CUTILS_DEBUG_TRACE
 #include "debug.h"
 #include "log.h"
@@ -9,6 +12,7 @@ int
 main (void)
 {
     char *ptr;
+    size_t len;
 
     ptr = malloc ((sizeof *ptr) * 1);
     ptr = realloc (ptr, (sizeof *ptr) * 4096);
@@ -22,5 +26,18 @@ main (void)
     log_print (LOG_LEVEL_DEBUG, "debug! %04.04f\n", 13.37);
     log_print_fl (LOG_LEVEL_OK, __FILE__, __LINE__, "file and line\n");
 
+    char s[] = "    Hello, World!\n    ";
+    len = strtrimr (s);
+    assert (len == 17);
+    assert (strlen (s) == 17);
+    char *sn = strtriml (s);
+    assert (sn == s + 4);
+    assert (strlen (sn) == 13);
+    char s2[] = "    Hello, World!\n    ";
+    sn = strtrim (s2);
+    assert (strlen (s2) == 17);
+    assert (sn == s2 + 4);
+    assert (strlen (sn) == 13);
+
     return EXIT_SUCCESS;
 }