Implement the PS4 variable which is defined by the POSIX User Portability

Utilities option.  Its value is printed at the beginning of the line if tracing
(-x) is active.  PS4 defaults to the string "+ " which is compatible with the
old behaviour to always print "+ ".

We still need to expand variables in PS1, PS2 and PS4.

PR:		46441 (part of)
Submitted by:	schweikh
Obtained from:	NetBSD

4 files changed, 23 insertions, 6 deletions

diff --git a/bin/sh/eval.c b/bin/sh/eval.c
index fa2fe59..dc0236d 100644
--- a/bin/sh/eval.c
+++ b/bin/sh/eval.c
@@ -643,14 +643,19 @@ evalcommand(union node *cmd, int flags, struct backcmd *backcmd)
 
 	/* Print the command if xflag is set. */
 	if (xflag) {
-		outc('+', &errout);
+		char sep = 0;
+		out2str(ps4val());
 		for (sp = varlist.list ; sp ; sp = sp->next) {
-			outc(' ', &errout);
+			if (sep != 0)
+				outc(' ', &errout);
 			out2str(sp->text);
+			sep = ' ';
 		}
 		for (sp = arglist.list ; sp ; sp = sp->next) {
-			outc(' ', &errout);
+			if (sep != 0)
+				outc(' ', &errout);
 			out2str(sp->text);
+			sep = ' ';
 		}
 		outc('\n', &errout);
 		flushout(&errout);
diff --git a/bin/sh/sh.1 b/bin/sh/sh.1
index 3c2fa9c..438fc24 100644
--- a/bin/sh/sh.1
+++ b/bin/sh/sh.1
@@ -32,7 +32,7 @@
 .\"	from: @(#)sh.1	8.6 (Berkeley) 5/4/95
 .\" $FreeBSD$
 .\"
-.Dd December 8, 2005
+.Dd June 15, 2006
 .Dt SH 1
 .Os
 .Sh NAME
@@ -305,8 +305,9 @@ as it is read.
 Useful for debugging.
 .It Fl x Li xtrace
 Write each command
-(preceded by
-.Dq Li "+ " )
+(preceded by the value of the 
+.Ev PS4
+variable)
 to standard error before it is executed.
 Useful for debugging.
 .El
@@ -2197,6 +2198,12 @@ unless you are the superuser, in which case it defaults to
 .It Ev PS2
 The secondary prompt string, which defaults to
 .Dq Li "> " .
+.It Ev PS4
+The prefix for the trace output (if
+.Fl x
+is active).
+The default is
+.Dq Li "+ " .
 .It Ev TERM
 The default terminal setting for the shell.
 This is inherited by children of the shell, and is used in the history
diff --git a/bin/sh/var.c b/bin/sh/var.c
index 4dc54b0..54a0a84 100644
--- a/bin/sh/var.c
+++ b/bin/sh/var.c
@@ -88,6 +88,7 @@ struct var vpath;
 struct var vppid;
 struct var vps1;
 struct var vps2;
+struct var vps4;
 struct var vvers;
 STATIC struct var voptind;
 
@@ -111,6 +112,8 @@ STATIC const struct varinit varinit[] = {
 	 */
 	{ &vps2,	VSTRFIXED|VTEXTFIXED,		"PS2=> ",
 	  NULL },
+	{ &vps4,	VSTRFIXED|VTEXTFIXED,		"PS4=+ ",
+	  NULL },
 	{ &voptind,	VSTRFIXED|VTEXTFIXED,		"OPTIND=1",
 	  getoptsreset },
 	{ NULL,	0,				NULL,
diff --git a/bin/sh/var.h b/bin/sh/var.h
index 4eb5dc1..c1f994b 100644
--- a/bin/sh/var.h
+++ b/bin/sh/var.h
@@ -74,6 +74,7 @@ extern struct var vpath;
 extern struct var vppid;
 extern struct var vps1;
 extern struct var vps2;
+extern struct var vps4;
 #ifndef NO_HISTORY
 extern struct var vhistsize;
 #endif
@@ -91,6 +92,7 @@ extern struct var vhistsize;
 #define pathval()	(vpath.text + 5)
 #define ps1val()	(vps1.text + 4)
 #define ps2val()	(vps2.text + 4)
+#define ps4val()	(vps4.text + 4)
 #define optindval()	(voptind.text + 7)
 #ifndef NO_HISTORY
 #define histsizeval()	(vhistsize.text + 9)