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ndb/dnsquery: make ! bang work with reverse lookups, document in ndb(8)

--- a/sys/man/8/ndb

+++ b/sys/man/8/ndb

@@ -683,6 +683,9 @@

 .I Ndb/dnsquery

 prompts for commands of the form

 .IP

+[

+.B !

+]

 .I "domain-name request-type"

 .LP

 where

@@ -700,6 +703,11 @@

 will reverse the ip address and tack on the

 .B .in-addr.arpa

 if necessary.

+If the command starts with an exclamation mark

+.B !

+then the response is returned in

+.IR ndb (6)

+format.

 The

 .B -x

 option switches

@@ -707,7 +715,7 @@

 to query the dns server on

 .B /net.alt

 instead of

-.B /net

+.BR /net .

 .PP

 .I Ndb/dnsdebug

 is like

--- a/sys/src/cmd/ndb/dnsquery.c

+++ b/sys/src/cmd/ndb/dnsquery.c

@@ -53,41 +53,47 @@

 query(int fd)

 {

 	int n;

-	char *lp;

+	char *lp, *bang;

 	char buf[1024], line[1024];

 	Biobuf in;

 	Binit(&in, 0, OREAD);

 	for(fprint(2, "> "); lp = Brdline(&in, '\n'); fprint(2, "> ")){

-		n = Blinelen(&in) -1;

-		while(isspace(lp[n]))

-			lp[n--] = 0;

-		n++;

-		while(isspace(*lp)){

-			lp++;

+		n = Blinelen(&in);

+		while(n > 0 && isspace(lp[n-1]))

 			n--;

+		lp[n] = 0;

+		while(isspace(*lp))

+			lp++;

+		bang = "";

+		while(*lp == '!'){

+			bang = "!";

+			lp++;

 		}

-		if(!*lp)

+		while(isspace(*lp))

+			lp++;

+		if(*lp == 0)

 			continue;

-		strcpy(line, lp);

 		/* default to an "ip" request if alpha, "ptr" if numeric */

-		if(strchr(line, ' ') == nil)

-			if(strcmp(ipattr(line), "ip") == 0) {

-				strcat(line, " ptr");

-				n += 4;

+		if(strchr(lp, ' ') == nil){

+			if(strcmp(ipattr(lp), "ip") == 0) {

+				n = snprint(line, sizeof line, "%s ptr", lp);

 			} else {

-				strcat(line, " ip");

-				n += 3;

+				n = snprint(line, sizeof line, "%s ip", lp);

 			}

+		} else {

+			n = snprint(line, sizeof line, "%s", lp);

+		}

 		if(n > 4 && strcmp(" ptr", &line[n-4]) == 0){

 			line[n-4] = 0;

 			mkptrname(line, buf, sizeof buf);

-			n = snprint(line, sizeof line, "%s ptr", buf);

+			snprint(line, sizeof line, "%s ptr", buf);

 		}

-		querydns(fd, line, n);

+		n = snprint(buf, sizeof buf, "%s%s", bang, line);

+		querydns(fd, buf, n);

 	}

 	Bterm(&in);

 }