Initial revision
diff --git a/src/libregexp/regsub.c b/src/libregexp/regsub.c
new file mode 100644
index 0000000..6de2c95
--- /dev/null
+++ b/src/libregexp/regsub.c
@@ -0,0 +1,62 @@
+#include "lib9.h"
+#include "regexp9.h"
+
+/* substitute into one string using the matches from the last regexec() */
+extern void
+regsub(char *sp, /* source string */
+ char *dp, /* destination string */
+ int dlen,
+ Resub *mp, /* subexpression elements */
+ int ms) /* number of elements pointed to by mp */
+{
+ char *ssp, *ep;
+ int i;
+
+ ep = dp+dlen-1;
+ while(*sp != '\0'){
+ if(*sp == '\\'){
+ switch(*++sp){
+ case '0':
+ case '1':
+ case '2':
+ case '3':
+ case '4':
+ case '5':
+ case '6':
+ case '7':
+ case '8':
+ case '9':
+ i = *sp-'0';
+ if(mp[i].s.sp != 0 && mp!=0 && ms>i)
+ for(ssp = mp[i].s.sp;
+ ssp < mp[i].e.ep;
+ ssp++)
+ if(dp < ep)
+ *dp++ = *ssp;
+ break;
+ case '\\':
+ if(dp < ep)
+ *dp++ = '\\';
+ break;
+ case '\0':
+ sp--;
+ break;
+ default:
+ if(dp < ep)
+ *dp++ = *sp;
+ break;
+ }
+ }else if(*sp == '&'){
+ if(mp[0].s.sp != 0 && mp!=0 && ms>0)
+ if(mp[0].s.sp != 0)
+ for(ssp = mp[0].s.sp;
+ ssp < mp[0].e.ep; ssp++)
+ if(dp < ep)
+ *dp++ = *ssp;
+ }else
+ if(dp < ep)
+ *dp++ = *sp;
+ sp++;
+ }
+ *dp = '\0';
+}
