Respect LC_CTYPE and LC_COLLATE environment variables, mainly for their

effects on regular expressions. The libc regex code does not handle
equivalence classes well (for example), but we do our best.

usr.bin/csplit/csplit.1

@@ -115,6 +115,17 @@ After all the patterns have been processed, the remaining input data
 .Pp
 Requesting to split at a line before the current line number or past the
 end of the file will result in an error.
+.Sh ENVIRONMENT
+The
+.Ev LANG ,
+.Ev LC_ALL ,
+.Ev LC_COLLATE
+and
+.Ev LC_CTYPE
+environment variables affect the execution of
+.Nm
+as described in
+.Xr environ 7 .
 .Sh EXAMPLES
 Split the
 .Xr mdoc 7

usr.bin/csplit/csplit.c

@@ -51,6 +51,7 @@ __FBSDID("$FreeBSD$");
 #include <err.h>
 #include <errno.h>
 #include <limits.h>
+#include <locale.h>
 #include <regex.h>
 #include <signal.h>
 #include <stdint.h>
@@ -99,6 +100,8 @@ main(int argc, char *argv[])
 	char *ep, *p;
 	FILE *ofp;
 
+	setlocale(LC_ALL, "");
+
 	kflag = sflag = 0;
 	prefix = "xx";
 	sufflen = 2;