Plan 9's rc.

not a clear win over byron's,
but at least it has the right syntax.

src/cmd/rc/haventfork.c

@@ -0,0 +1,211 @@
+#include "rc.h"
+#include "getflags.h"
+#include "exec.h"
+#include "io.h"
+#include "fns.h"
+
+int havefork = 0;
+
+static char **
+rcargv(char *s)
+{
+	int argc;
+	char **argv;
+	word *p;
+
+	p = vlook("*")->val;
+	argv = malloc((count(p)+6)*sizeof(char*));
+	argc = 0;
+	argv[argc++] = argv0;
+	if(flag['e'])
+		argv[argc++] = "-Se";
+	else
+		argv[argc++] = "-S";
+	argv[argc++] = "-c";
+	argv[argc++] = s;
+	for(p = vlook("*")->val; p; p = p->next)
+		argv[argc++] = p->word;
+	argv[argc] = 0;
+	return argv;
+}
+
+void
+Xasync(void)
+{
+	uint pid;
+	char buf[20], **argv;
+
+	Updenv();
+
+	argv = rcargv(runq->code[runq->pc].s);
+	pid = ForkExecute(argv0, argv, -1, 1, 2);
+	free(argv);
+
+	if(pid == 0) {
+		Xerror("proc failed");
+		return;
+	}
+
+	runq->pc++;
+	sprint(buf, "%d", pid);
+	setvar("apid", newword(buf, (word *)0));
+}
+
+void
+Xbackq(void)
+{
+	char wd[8193], **argv;
+	int c;
+	char *s, *ewd=&wd[8192], *stop;
+	struct io *f;
+	var *ifs = vlook("ifs");
+	word *v, *nextv;
+	int pfd[2];
+	int pid;
+
+	stop = ifs->val?ifs->val->word:"";
+	if(pipe(pfd)<0){
+		Xerror("can't make pipe");
+		return;
+	}
+
+	Updenv();
+
+	argv = rcargv(runq->code[runq->pc].s);
+	pid = ForkExecute(argv0, argv, -1, pfd[1], 2);
+	free(argv);
+
+	close(pfd[1]);
+
+	if(pid == 0) {
+		Xerror("proc failed");
+		close(pfd[0]);
+		return;
+	}
+
+	f = openfd(pfd[0]);
+	s = wd;
+	v = 0;
+	while((c=rchr(f))!=EOF){
+		if(strchr(stop, c) || s==ewd){
+			if(s!=wd){
+				*s='\0';
+				v=newword(wd, v);
+				s=wd;
+			}
+		}
+		else *s++=c;
+	}
+	if(s!=wd){
+		*s='\0';
+		v=newword(wd, v);
+	}
+	closeio(f);
+	Waitfor(pid, 1);
+	/* v points to reversed arglist -- reverse it onto argv */
+	while(v){
+		nextv=v->next;
+		v->next=runq->argv->words;
+		runq->argv->words=v;
+		v=nextv;
+	}
+	runq->pc++;
+}
+
+void
+Xpipe(void)
+{
+	thread *p=runq;
+	int pc=p->pc, pid;
+	int rfd=p->code[pc+1].i;
+	int pfd[2];
+	char **argv;
+
+	if(pipe(pfd)<0){
+		Xerror1("can't get pipe");
+		return;
+	}
+
+	Updenv();
+
+	argv = rcargv(runq->code[pc+2].s);
+	pid = ForkExecute(argv0, argv, 0, pfd[1], 2);
+	free(argv);
+	close(pfd[1]);
+
+	if(pid == 0) {
+		Xerror("proc failed");
+		close(pfd[0]);
+		return;
+	}
+
+	start(p->code, pc+4, runq->local);
+	pushredir(ROPEN, pfd[0], rfd);
+	p->pc=p->code[pc+3].i;
+	p->pid=pid;
+}
+
+void
+Xpipefd(void)
+{
+	Abort();
+}
+
+void
+Xsubshell(void)
+{
+	char **argv;
+	int pid;
+
+	Updenv();
+
+	argv = rcargv(runq->code[runq->pc].s);
+	pid = ForkExecute(argv0, argv, -1, 1, 2);
+	free(argv);
+
+	if(pid < 0) {
+		Xerror("proc failed");
+		return;
+	}
+
+	Waitfor(pid, 1);
+	runq->pc++;
+}
+
+/*
+ *  start a process running the cmd on the stack and return its pid.
+ */
+int
+execforkexec(void)
+{
+	char **argv;
+	char file[1024];
+	int nc;
+	word *path;
+	int pid;
+
+	if(runq->argv->words==0)
+		return -1;
+	argv = mkargv(runq->argv->words);
+
+	for(path = searchpath(runq->argv->words->word);path;path = path->next){
+		nc = strlen(path->word);
+		if(nc<sizeof(file)){
+			strcpy(file, path->word);
+			if(file[0]){
+				strcat(file, "/");
+				nc++;
+			}
+			if(nc+strlen(argv[1])<sizeof(file)){
+				strcat(file, argv[1]);
+				pid = ForkExecute(file, argv+1, mapfd(0), mapfd(1), mapfd(2));
+				if(pid >= 0){
+					free(argv);
+					return pid;
+				}
+			}
+		}
+	}
+	free(argv);
+	return -1;
+}