+.SH NOTES
+The
+.BR strcasecmp ()
+and
+.BR strncasecmp ()
+functions first appeared in 4.4BSD, where they were declared in
+.IR <string.h> .
+Thus, for reasons of historical compatibility, the glibc
+.I <string.h>
+header file also declares these functions, if the
+.B _DEFAULT_SOURCE
+(or, in glibc 2.19 and earlier,
+.BR _BSD_SOURCE )
+feature test macro is defined.