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From: nnd@itfs.nsk.su (Nickolay N. Dudorov)
To: hackers@freebsd.org
Subject: (Very) Old bug in /bin/sh (ash ?)
Message-ID: <DJ4994.C2J@itfs.nsk.su>
Date: Tue, 5 Dec 1995 13:53:27 GMT
Sender: owner-hackers@freebsd.org
Precedence: bulk

	On all 'sh'-ells here (SysV.3.2, SunOS 4.1.3 etc)
construction:

	{ a; b; c & d; e; }

is parsed and evaluated as a list of simple commands and one of
them (namely - c) is executed 'in background' or 'asynchronously'.

	But on the FreeBSD systems (versions from 1.1 to 2.1)
it is parsed and evaluated as:

	{ { a; b; c; } & { d; e; } }


	Is this a BUG or a FEATURE ?

It seems to me that it is a bug in 'ash'. Following is a fix
for this misbehavior.
(This diff -u command was executed in /usr/src/bin/sh directory
on 2.1-STABLE sources SUP-ed until yesterday).

	N.Dudorov
====================================================================
--- parser.c.ORG	Tue Dec  5 16:15:52 1995
+++ parser.c	Tue Dec  5 18:50:22 1995
@@ -149,30 +149,13 @@
 	n1 = andor();
 	for (;;) {
 		switch (readtoken()) {
-		case TBACKGND:
-			if (n1->type == NCMD || n1->type == NPIPE) {
-				n1->ncmd.backgnd = 1;
-			} else if (n1->type == NREDIR) {
-				n1->type = NBACKGND;
-			} else {
-				n3 = (union node *)stalloc(sizeof (struct nredir));
-				n3->type = NBACKGND;
-				n3->nredir.n = n1;
-				n3->nredir.redirect = NULL;
-				n1 = n3;
-			}
-			goto tsemi;
 		case TNL:
-			tokpushback++;
+			parseheredoc();
+			if (nlflag)
+				return n1;
 			/* fall through */
-tsemi:	    case TSEMI:
-			if (readtoken() == TNL) {
-				parseheredoc();
-				if (nlflag)
-					return n1;
-			} else {
-				tokpushback++;
-			}
+		case TBACKGND:
+		case TSEMI:
 			checkkwd = 2;
 			if (tokendlist[peektoken()])
 				return n1;
@@ -212,6 +195,19 @@
 		} else if (t == TOR) {
 			t = NOR;
 		} else {
+			if (t == TBACKGND) {
+				if (n1->type == NCMD || n1->type == NPIPE) {
+					n1->ncmd.backgnd = 1;
+				} else if (n1->type == NREDIR) {
+					n1->type = NBACKGND;
+				} else {
+					n3 = (union node *)stalloc(sizeof (struct nredir));
+					n3->type = NBACKGND;
+					n3->nredir.n = n1;
+					n3->nredir.redirect = NULL;
+					n1 = n3;
+				}
+			}
 			tokpushback++;
 			return n1;
 		}