With these changes sh(1)'s trap command should be POSIX-compliant,

while remaining (becoming :) compatible with other popular shells.
Specifically these changes include:

1) Implement 'trap -l' to get a list of valid signals names.  This
   is useful if you wanted to do something like reset all signal
   handlers to there defaults values, in which case something like
   this will do the trick.

	trap `trap -l`

2) Reformat the output of 'trap' so it can be saved and later eval'd
   to restore the saved settings.

3) Allow the use of signal names as well as signal numbers.

4) Fix trap handling of SIGCHLD so that commands like the following
   (albeit, contrived) won't cause sh(1) to recurse ad infinitum.

	trap uname 0 20

5) Make variables static that are used only in trap.c.

6) Minor 'style(9) police' mods.

1 files changed, 107 insertions, 49 deletions

diff --git a/bin/sh/trap.c b/bin/sh/trap.c
index 5b99d42..7fe98a3 100644
--- a/bin/sh/trap.c
+++ b/bin/sh/trap.c
@@ -33,7 +33,7 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- *	$Id: trap.c,v 1.4 1996/09/01 10:21:47 peter Exp $
+ *	$Id: trap.c,v 1.5 1996/12/14 06:19:32 steve Exp $
  */
 
 #ifndef lint
@@ -72,43 +72,99 @@ static char const sccsid[] = "@(#)trap.c	8.5 (Berkeley) 6/5/95";
 #define S_RESET 5		/* temporary - to reset a hard ignored sig */
 
 
-extern char nullstr[1];		/* null string */
-
-char *trap[NSIG+1];		/* trap handler commands */
 MKINIT char sigmode[NSIG];	/* current value of signal */
-char gotsig[NSIG];		/* indicates specified signal received */
 int pendingsigs;			/* indicates some signal received */
+static char *trap[NSIG];	/* trap handler commands */
+static char gotsig[NSIG];	/* indicates specified signal received */
+static int ignore_sigchld;	/* Used while handling SIGCHLD traps. */
 
 static int getsigaction __P((int, sig_t *));
 
+
 /*
- * The trap builtin.
+ * Map a string to a signal number.
  */
+static int
+sigstring_to_signum(sig)
+	char *sig;
+{
+
+	if (is_number(sig)) {
+		int signo;
+
+		signo = atoi(sig);
+		return ((signo >= 0 && signo < NSIG) ? signo : (-1));
+	} else if (strcasecmp(sig, "exit") == 0) {
+		return (0);
+	} else {
+		int n;
+
+		if (strncasecmp(sig, "sig", 3) == 0)
+			sig += 3;
+		for (n = 1; n < NSIG; n++)
+			if (strcasecmp(sys_signame[n], sig) == 0)
+				return (n);
+	}
+	return (-1);
+}
+
 
+/*
+ * Print a list of valid signal names.
+ */
+static void
+printsignals()
+{
+	int n;
+
+	for (n = 1; n < NSIG; n++) {
+		out1fmt("%s", sys_signame[n]);
+		if (n == (NSIG / 2) || n == (NSIG - 1))
+			out1str("\n");
+		else
+			out1c(' ');
+	}
+}
+
+
+/*
+ * The trap builtin.
+ */
 int
 trapcmd(argc, argv)
 	int argc;
 	char **argv;
 {
 	char *action;
-	char **ap;
 	int signo;
 
 	if (argc <= 1) {
-		for (signo = 0 ; signo <= NSIG ; signo++) {
+		for (signo = 0 ; signo < NSIG ; signo++) {
 			if (trap[signo] != NULL)
-				out1fmt("%d: %s\n", signo, trap[signo]);
+				out1fmt("trap -- '%s' %s\n", trap[signo],
+					(signo) ? sys_signame[signo] : "exit");
 		}
 		return 0;
 	}
-	ap = argv + 1;
-	if (is_number(*ap))
-		action = NULL;
-	else
-		action = *ap++;
-	while (*ap) {
-		if ((signo = number(*ap)) < 0 || signo > NSIG)
-			error("%s: bad trap", *ap);
+	action = NULL;
+	if (*++argv && strcmp(*argv, "--") == 0)
+		argv++;
+	if (*argv && sigstring_to_signum(*argv) == -1) {
+		if ((*argv)[0] != '-') {
+			action = *argv;
+			argv++;
+		} else if ((*argv)[1] == '\0') {
+			argv++;
+		} else if ((*argv)[1] == 'l' && (*argv)[2] == '\0') {
+			printsignals();
+			return 0;
+		} else {
+			error("bad option %s", *argv);
+		}
+	}
+	while (*argv) {
+		if ((signo = sigstring_to_signum(*argv)) == -1)
+			error("bad signal %s", *argv);
 		INTOFF;
 		if (action)
 			action = savestr(action);
@@ -118,22 +174,21 @@ trapcmd(argc, argv)
 		if (signo != 0)
 			setsignal(signo);
 		INTON;
-		ap++;
+		argv++;
 	}
 	return 0;
 }
 
 
-
 /*
  * Clear traps on a fork.
  */
-
 void
-clear_traps() {
+clear_traps()
+{
 	char **tp;
 
-	for (tp = trap ; tp <= &trap[NSIG] ; tp++) {
+	for (tp = trap ; tp <= &trap[NSIG - 1] ; tp++) {
 		if (*tp && **tp) {	/* trap not NULL or SIG_IGN */
 			INTOFF;
 			ckfree(*tp);
@@ -146,12 +201,10 @@ clear_traps() {
 }
 
 
-
 /*
  * Set the signal handler for the specified signal.  The routine figures
  * out what it should be set to.
  */
-
 long
 setsignal(signo)
 	int signo;
@@ -159,7 +212,6 @@ setsignal(signo)
 	int action;
 	sig_t sigact = SIG_DFL;
 	char *t;
-	extern void onsig();
 
 	if ((t = trap[signo]) == NULL)
 		action = S_DFL;
@@ -197,7 +249,7 @@ setsignal(signo)
 		}
 	}
 
-	t = &sigmode[signo - 1];
+	t = &sigmode[signo];
 	if (*t == 0) {
 		/*
 		 * current setting unknown
@@ -231,6 +283,7 @@ setsignal(signo)
 	return (long)signal(signo, sigact);
 }
 
+
 /*
  * Return the current setting for sig w/o changing it.
  */
@@ -247,18 +300,19 @@ getsigaction(signo, sigact)
 	return 1;
 }
 
+
 /*
  * Ignore a signal.
  */
-
 void
 ignoresig(signo)
 	int signo;
 {
-	if (sigmode[signo - 1] != S_IGN && sigmode[signo - 1] != S_HARD_IGN) {
+
+	if (sigmode[signo] != S_IGN && sigmode[signo] != S_HARD_IGN) {
 		signal(signo, SIG_IGN);
 	}
-	sigmode[signo - 1] = S_HARD_IGN;
+	sigmode[signo] = S_HARD_IGN;
 }
 
 
@@ -278,59 +332,65 @@ SHELLPROC {
 #endif
 
 
-
 /*
  * Signal handler.
  */
-
 void
 onsig(signo)
 	int signo;
 {
+
 	signal(signo, onsig);
 	if (signo == SIGINT && trap[SIGINT] == NULL) {
 		onint();
 		return;
 	}
-	gotsig[signo - 1] = 1;
+	if (signo != SIGCHLD || !ignore_sigchld)
+		gotsig[signo] = 1;
 	pendingsigs++;
 }
 
 
-
 /*
  * Called to execute a trap.  Perhaps we should avoid entering new trap
  * handlers while we are executing a trap handler.
  */
-
 void
-dotrap() {
+dotrap()
+{
 	int i;
 	int savestatus;
 
 	for (;;) {
-		for (i = 1 ; ; i++) {
-			if (gotsig[i - 1])
+		for (i = 1; i < NSIG; i++) {
+			if (gotsig[i]) {
+				gotsig[i] = 0;
+				if (trap[i]) {
+					/*
+					 * Ignore SIGCHLD to avoid infinite recursion
+					 * if the trap action does a fork.
+					 */
+					if (i == SIGCHLD)
+						ignore_sigchld++;
+					savestatus = exitstatus;
+					evalstring(trap[i]);
+					exitstatus = savestatus;
+					if (i == SIGCHLD)
+						ignore_sigchld--;
+				}
 				break;
-			if (i >= NSIG)
-				goto done;
+			}
 		}
-		gotsig[i - 1] = 0;
-		savestatus=exitstatus;
-		evalstring(trap[i]);
-		exitstatus=savestatus;
+		if (i >= NSIG)
+			break;
 	}
-done:
 	pendingsigs = 0;
 }
 
 
-
 /*
  * Controls whether the shell is interactive or not.
  */
-
-
 void
 setinteractive(on)
 	int on;
@@ -346,11 +406,9 @@ setinteractive(on)
 }
 
 
-
 /*
  * Called to exit the shell.
  */
-
 void
 exitshell(status)
 	int status;