Include hostname in shell prompts by default

With tmux, ssh and vmd, we tend to open shells on many different hosts
simultaneously and the default prompts '$ ' and '# ' for {,k}sh as well
as  '% ' and '# ' for csh become dangerous: it's very easy to issue a
command on the wrong host.

This can easily be avoided by displaying the hostname in the prompt.
Everything beyond "hostname{$,#,%} " is going to be a matter of taste,
so we left it at that. If you use an FQDN, only the first part (the
output of 'hostname -s') will be printed.

requested by and ok deraadt; mostly positive feedback many
ok anton, brynet, bcallah and others

4 files changed, 20 insertions, 10 deletions

diff --git a/bin/csh/const.c b/bin/csh/const.c
index 9307f2d370d..532c74b63fa 100644
--- a/bin/csh/const.c
+++ b/bin/csh/const.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: const.c,v 1.8 2015/10/26 16:27:04 naddy Exp $	*/
+/*	$OpenBSD: const.c,v 1.9 2017/12/12 00:18:58 tb Exp $	*/
 /*	$NetBSD: const.c,v 1.6 1995/03/21 09:02:31 cgd Exp $	*/
 
 /*-
@@ -114,6 +114,8 @@ Char STRprintexitvalue[] = { 'p', 'r', 'i', 'n', 't', 'e', 'x', 'i', 't', 'v',
 			    'a', 'l', 'u', 'e', '\0' };
 Char STRprompt[]	= { 'p', 'r', 'o', 'm', 'p', 't', '\0' };
 Char STRprompt2[]	= { 'p', 'r', 'o', 'm', 'p', 't', '2', '\0' };
+Char STRpromptroot[]	= { '%', 'm', '#', ' ', '\0' };
+Char STRpromptuser[]	= { '%', 'm', '%', ' ', '\0' };
 Char STRpushdsilent[]	= { 'p', 'u', 's', 'h', 'd', 's', 'i', 'l', 'e', 'n',
 			    't', '\0' };
 Char STRret[]		= { '\n', '\0' };
@@ -138,8 +140,6 @@ Char STRspor2sp[]	= { ' ', '|', '|', ' ', '\0' };
 Char STRsporsp[]	= { ' ', '|', ' ', '\0' };
 Char STRstar[]		= { '*', '\0' };
 Char STRstatus[]	= { 's', 't', 'a', 't', 'u', 's', '\0' };
-Char STRsymcent[]	= { '%', ' ', '\0' };
-Char STRsymhash[]	= { '#', ' ', '\0' };
 Char STRterm[]		= { 't', 'e', 'r', 'm', '\0' };
 Char STRthen[]		= { 't', 'h', 'e', 'n', '\0' };
 Char STRtilde[]		= { '~', '\0' };
diff --git a/bin/csh/csh.c b/bin/csh/csh.c
index 5df655ade5d..d737c31ab30 100644
--- a/bin/csh/csh.c
+++ b/bin/csh/csh.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: csh.c,v 1.41 2017/08/30 06:42:21 anton Exp $	*/
+/*	$OpenBSD: csh.c,v 1.42 2017/12/12 00:18:58 tb Exp $	*/
 /*	$NetBSD: csh.c,v 1.14 1995/04/29 23:21:28 mycroft Exp $	*/
 
 /*-
@@ -401,7 +401,7 @@ main(int argc, char *argv[])
      * Set up the prompt.
      */
     if (prompt) {
-	set(STRprompt, Strsave(uid == 0 ? STRsymhash : STRsymcent));
+	set(STRprompt, Strsave(uid == 0 ? STRpromptroot : STRpromptuser));
 	/* that's a meta-questionmark */
 	set(STRprompt2, Strsave(STRmquestion));
     }
@@ -1283,7 +1283,16 @@ printprompt(void)
 	for (cp = value(STRprompt); *cp; cp++)
 	    if (*cp == HIST)
 		(void) fprintf(cshout, "%d", eventno + 1);
-	    else {
+	    else if (*cp == '%' && *(cp + 1) == 'm') {
+		char hostname[HOST_NAME_MAX + 1];
+		char *p;
+
+		gethostname(hostname, sizeof hostname);
+		if ((p = strchr(hostname, '.')) != NULL)
+		    *p = '\0';
+		fprintf(cshout, "%s", hostname);
+		cp++;
+	    } else {
 		if (*cp == '\\' && cp[1] == HIST)
 		    cp++;
 		(void) vis_fputc(*cp | QUOTE, cshout);
diff --git a/bin/ksh/lex.c b/bin/ksh/lex.c
index db32396fb92..858eb898cbf 100644
--- a/bin/ksh/lex.c
+++ b/bin/ksh/lex.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: lex.c,v 1.72 2017/12/07 01:54:33 tb Exp $	*/
+/*	$OpenBSD: lex.c,v 1.73 2017/12/12 00:18:58 tb Exp $	*/
 
 /*
  * lexical analysis and source input
@@ -1246,7 +1246,8 @@ dopprompt(const char *sp, int ntruncate, const char **spp, int doprint)
 			cp++;
 			if (!*cp)
 				break;
-			if (Flag(FSH))
+			/* Expand \h and \$ for both, sh(1) and ksh(1) */
+			if (Flag(FSH) && !(*cp == 'h' || *cp == 'p'))
 				snprintf(strbuf, sizeof strbuf, "\\%c", *cp);
 			else switch (*cp) {
 			case 'a':	/* '\' 'a' bell */
diff --git a/bin/ksh/main.c b/bin/ksh/main.c
index eef7e3041ae..5676d63133a 100644
--- a/bin/ksh/main.c
+++ b/bin/ksh/main.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: main.c,v 1.84 2017/12/07 01:54:33 tb Exp $	*/
+/*	$OpenBSD: main.c,v 1.85 2017/12/12 00:18:58 tb Exp $	*/
 
 /*
  * startup, main loop, environments and error handling
@@ -316,7 +316,7 @@ main(int argc, char *argv[])
 		/* Set PS1 if it isn't set */
 		if (!(vp->flag & ISSET)) {
 			/* setstr can't fail here */
-			setstr(vp, safe_prompt, KSH_RETURN_ERROR);
+			setstr(vp, "\\h\\$ ", KSH_RETURN_ERROR);
 		}
 	}