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

1 files changed, 8 insertions, 3 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);