Plan 9's rc.

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

1 files changed, 902 insertions, 0 deletions

diff --git a/src/cmd/rc/exec.c b/src/cmd/rc/exec.c
new file mode 100644
index 00000000..ebed11d8
--- /dev/null
+++ b/src/cmd/rc/exec.c
@@ -0,0 +1,902 @@
+#include "rc.h"
+#include "getflags.h"
+#include "exec.h"
+#include "io.h"
+#include "fns.h"
+/*
+ * Start executing the given code at the given pc with the given redirection
+ */
+char *argv0="rc";
+void start(code *c, int pc, var *local)
+{
+	struct thread *p=new(struct thread);
+	p->code=codecopy(c);
+	p->pc=pc;
+	p->argv=0;
+	p->redir=p->startredir=runq?runq->redir:0;
+	p->local=local;
+	p->cmdfile=0;
+	p->cmdfd=0;
+	p->eof=0;
+	p->iflag=0;
+	p->lineno=1;
+	p->ret=runq;
+	runq=p;
+}
+word *newword(char *wd, word *next)
+{
+	word *p=new(word);
+	p->word=strdup(wd);
+	p->next=next;
+	return p;
+}
+void pushword(char *wd)
+{
+	if(runq->argv==0) panic("pushword but no argv!", 0);
+	runq->argv->words=newword(wd, runq->argv->words);
+}
+void popword(void){
+	word *p;
+	if(runq->argv==0) panic("popword but no argv!", 0);
+	p=runq->argv->words;
+	if(p==0) panic("popword but no word!", 0);
+	runq->argv->words=p->next;
+	efree(p->word);
+	efree((char *)p);
+}
+void freelist(word *w)
+{
+	word *nw;
+	while(w){
+		nw=w->next;
+		efree(w->word);
+		efree((char *)w);
+		w=nw;
+	}
+}
+void pushlist(void){
+	list *p=new(list);
+	p->next=runq->argv;
+	p->words=0;
+	runq->argv=p;
+}
+void poplist(void){
+	list *p=runq->argv;
+	if(p==0) panic("poplist but no argv", 0);
+	freelist(p->words);
+	runq->argv=p->next;
+	efree((char *)p);
+}
+int count(word *w)
+{
+	int n;
+	for(n=0;w;n++) w=w->next;
+	return n;
+}
+void pushredir(int type, int from, int to){
+	redir * rp=new(redir);
+	rp->type=type;
+	rp->from=from;
+	rp->to=to;
+	rp->next=runq->redir;
+	runq->redir=rp;
+}
+var *newvar(char *name, var *next)
+{
+	var *v=new(var);
+	v->name=name;
+	v->val=0;
+	v->fn=0;
+	v->changed=0;
+	v->fnchanged=0;
+	v->next=next;
+	return v;
+}
+/*
+ * get command line flags, initialize keywords & traps.
+ * get values from environment.
+ * set $pid, $cflag, $*
+ * fabricate bootstrap code and start it (*=(argv);. /usr/lib/rcmain $*)
+ * start interpreting code
+ */
+int
+main(int argc, char *argv[])
+{
+	code bootstrap[32];
+	char num[12], *rcmain;
+	int i;
+
+	argc=getflags(argc, argv, "srdiIlxepvVc:1m:1[command]", 1);
+	if(argc==-1) usage("[file [arg ...]]");
+	if(argv[0][0]=='-') flag['l']=flagset;
+	if(flag['I']) flag['i'] = 0;
+	else if(flag['i']==0 && argc==1 && Isatty(0)) flag['i'] = flagset;
+	rcmain=flag['m']?flag['m'][0]:Rcmain(); 
+	err=openfd(2);
+	kinit();
+	Trapinit();
+	Vinit();
+	itoa(num, mypid=getpid());
+	setvar("pid", newword(num, (word *)0));
+	setvar("cflag", flag['c']?newword(flag['c'][0], (word *)0)
+				:(word *)0);
+	setvar("rcname", newword(argv[0], (word *)0));
+	i=0;
+	bootstrap[i++].i=1;
+	bootstrap[i++].f=Xmark;
+	bootstrap[i++].f=Xword;
+	bootstrap[i++].s="*";
+	bootstrap[i++].f=Xassign;
+	bootstrap[i++].f=Xmark;
+	bootstrap[i++].f=Xmark;
+	bootstrap[i++].f=Xword;
+	bootstrap[i++].s="*";
+	bootstrap[i++].f=Xdol;
+	bootstrap[i++].f=Xword;
+	bootstrap[i++].s=rcmain;
+	bootstrap[i++].f=Xword;
+	bootstrap[i++].s=".";
+	bootstrap[i++].f=Xsimple;
+	bootstrap[i++].f=Xexit;
+	bootstrap[i].i=0;
+	start(bootstrap, 1, (var *)0);
+	/* prime bootstrap argv */
+	pushlist();
+	argv0 = strdup(argv[0]);
+	for(i=argc-1;i!=0;--i) pushword(argv[i]);
+	for(;;){
+		if(flag['r']) pfnc(err, runq);
+		runq->pc++;
+		(*runq->code[runq->pc-1].f)();
+		if(ntrap) dotrap();
+	}
+}
+/*
+ * Opcode routines
+ * Arguments on stack (...)
+ * Arguments in line [...]
+ * Code in line with jump around {...}
+ *
+ * Xappend(file)[fd]			open file to append
+ * Xassign(name, val)			assign val to name
+ * Xasync{... Xexit}			make thread for {}, no wait
+ * Xbackq{... Xreturn}			make thread for {}, push stdout
+ * Xbang				complement condition
+ * Xcase(pat, value){...}		exec code on match, leave (value) on
+ * 					stack
+ * Xclose[i]				close file descriptor
+ * Xconc(left, right)			concatenate, push results
+ * Xcount(name)				push var count
+ * Xdelfn(name)				delete function definition
+ * Xdeltraps(names)			delete named traps
+ * Xdol(name)				get variable value
+ * Xqdol(name)				concatenate variable components
+ * Xdup[i j]				dup file descriptor
+ * Xexit				rc exits with status
+ * Xfalse{...}				execute {} if false
+ * Xfn(name){... Xreturn}			define function
+ * Xfor(var, list){... Xreturn}		for loop
+ * Xjump[addr]				goto
+ * Xlocal(name, val)			create local variable, assign value
+ * Xmark				mark stack
+ * Xmatch(pat, str)			match pattern, set status
+ * Xpipe[i j]{... Xreturn}{... Xreturn}	construct a pipe between 2 new threads,
+ * 					wait for both
+ * Xpipefd[type]{... Xreturn}		connect {} to pipe (input or output,
+ * 					depending on type), push /dev/fd/??
+ * Xpopm(value)				pop value from stack
+ * Xread(file)[fd]			open file to read
+ * Xsettraps(names){... Xreturn}		define trap functions
+ * Xshowtraps				print trap list
+ * Xsimple(args)			run command and wait
+ * Xreturn				kill thread
+ * Xsubshell{... Xexit}			execute {} in a subshell and wait
+ * Xtrue{...}				execute {} if true
+ * Xunlocal				delete local variable
+ * Xword[string]			push string
+ * Xwrite(file)[fd]			open file to write
+ */
+void Xappend(void){
+	char *file;
+	int f;
+	switch(count(runq->argv->words)){
+	default: Xerror1(">> requires singleton"); return;
+	case 0: Xerror1(">> requires file"); return;
+	case 1: break;
+	}
+	file=runq->argv->words->word;
+	if((f=open(file, 1))<0 && (f=Creat(file))<0){
+		pfmt(err, "%s: ", file);
+		Xerror("can't open");
+		return;
+	}
+	Seek(f, 0L, 2);
+	pushredir(ROPEN, f, runq->code[runq->pc].i);
+	runq->pc++;
+	poplist();
+}
+void Xasync(void){
+	int null=open("/dev/null", 0);
+	int pid;
+	char npid[10];
+	if(null<0){
+		Xerror("Can't open /dev/null\n");
+		return;
+	}
+	switch(pid=rfork(RFFDG|RFPROC|RFNOTEG)){
+	case -1:
+		close(null);
+		Xerror("try again");
+		break;
+	case 0:
+		pushredir(ROPEN, null, 0);
+		start(runq->code, runq->pc+1, runq->local);
+		runq->ret=0;
+		break;
+	default:
+		close(null);
+		runq->pc=runq->code[runq->pc].i;
+		itoa(npid, pid);
+		setvar("apid", newword(npid, (word *)0));
+		break;
+	}
+}
+void Xsettrue(void){
+	setstatus("");
+}
+void Xbang(void){
+	setstatus(truestatus()?"false":"");
+}
+void Xclose(void){
+	pushredir(RCLOSE, runq->code[runq->pc].i, 0);
+	runq->pc++;
+}
+void Xdup(void){
+	pushredir(RDUP, runq->code[runq->pc].i, runq->code[runq->pc+1].i);
+	runq->pc+=2;
+}
+void Xeflag(void){
+	if(eflagok && !truestatus()) Xexit();
+}
+void Xexit(void){
+	struct var *trapreq;
+	struct word *starval;
+	static int beenhere=0;
+	if(getpid()==mypid && !beenhere){
+		trapreq=vlook("sigexit");
+		if(trapreq->fn){
+			beenhere=1;
+			--runq->pc;
+			starval=vlook("*")->val;
+			start(trapreq->fn, trapreq->pc, (struct var *)0);
+			runq->local=newvar(strdup("*"), runq->local);
+			runq->local->val=copywords(starval, (struct word *)0);
+			runq->local->changed=1;
+			runq->redir=runq->startredir=0;
+			return;
+		}
+	}
+	Exit(getstatus());
+}
+void Xfalse(void){
+	if(truestatus()) runq->pc=runq->code[runq->pc].i;
+	else runq->pc++;
+}
+int ifnot;		/* dynamic if not flag */
+void Xifnot(void){
+	if(ifnot)
+		runq->pc++;
+	else
+		runq->pc=runq->code[runq->pc].i;
+}
+void Xjump(void){
+	runq->pc=runq->code[runq->pc].i;
+}
+void Xmark(void){
+	pushlist();
+}
+void Xpopm(void){
+	poplist();
+}
+void Xread(void){
+	char *file;
+	int f;
+	switch(count(runq->argv->words)){
+	default: Xerror1("< requires singleton\n"); return;
+	case 0: Xerror1("< requires file\n"); return;
+	case 1: break;
+	}
+	file=runq->argv->words->word;
+	if((f=open(file, 0))<0){
+		pfmt(err, "%s: ", file);
+		Xerror("can't open");
+		return;
+	}
+	pushredir(ROPEN, f, runq->code[runq->pc].i);
+	runq->pc++;
+	poplist();
+}
+void turfredir(void){
+	while(runq->redir!=runq->startredir)
+		Xpopredir();
+}
+void Xpopredir(void){
+	struct redir *rp=runq->redir;
+	if(rp==0) panic("turfredir null!", 0);
+	runq->redir=rp->next;
+	if(rp->type==ROPEN) close(rp->from);
+	efree((char *)rp);
+}
+void Xreturn(void){
+	struct thread *p=runq;
+	turfredir();
+	while(p->argv) poplist();
+	codefree(p->code);
+	runq=p->ret;
+	efree((char *)p);
+	if(runq==0) Exit(getstatus());
+}
+void Xtrue(void){
+	if(truestatus()) runq->pc++;
+	else runq->pc=runq->code[runq->pc].i;
+}
+void Xif(void){
+	ifnot=1;
+	if(truestatus()) runq->pc++;
+	else runq->pc=runq->code[runq->pc].i;
+}
+void Xwastrue(void){
+	ifnot=0;
+}
+void Xword(void){
+	pushword(runq->code[runq->pc++].s);
+}
+void Xwrite(void){
+	char *file;
+	int f;
+	switch(count(runq->argv->words)){
+	default: Xerror1("> requires singleton\n"); return;
+	case 0: Xerror1("> requires file\n"); return;
+	case 1: break;
+	}
+	file=runq->argv->words->word;
+	if((f=Creat(file))<0){
+		pfmt(err, "%s: ", file);
+		Xerror("can't open");
+		return;
+	}
+	pushredir(ROPEN, f, runq->code[runq->pc].i);
+	runq->pc++;
+	poplist();
+}
+char *list2str(word *words){
+	char *value, *s, *t;
+	int len=0;
+	word *ap;
+	for(ap=words;ap;ap=ap->next)
+		len+=1+strlen(ap->word);
+	value=emalloc(len+1);
+	s=value;
+	for(ap=words;ap;ap=ap->next){
+		for(t=ap->word;*t;) *s++=*t++;
+		*s++=' ';
+	}
+	if(s==value) *s='\0';
+	else s[-1]='\0';
+	return value;
+}
+void Xmatch(void){
+	word *p;
+	char *subject;
+	subject=list2str(runq->argv->words);
+	setstatus("no match");
+	for(p=runq->argv->next->words;p;p=p->next)
+		if(match(subject, p->word, '\0')){
+			setstatus("");
+			break;
+		}
+	efree(subject);
+	poplist();
+	poplist();
+}
+void Xcase(void){
+	word *p;
+	char *s;
+	int ok=0;
+	s=list2str(runq->argv->next->words);
+	for(p=runq->argv->words;p;p=p->next){
+		if(match(s, p->word, '\0')){
+			ok=1;
+			break;
+		}
+	}
+	efree(s);
+	if(ok)
+		runq->pc++;
+	else
+		runq->pc=runq->code[runq->pc].i;
+	poplist();
+}
+word *conclist(word *lp, word *rp, word *tail)
+{
+	char *buf;
+	word *v;
+	if(lp->next || rp->next)
+		tail=conclist(lp->next==0?lp:lp->next, rp->next==0?rp:rp->next,
+			tail);
+	buf=emalloc(strlen(lp->word)+strlen(rp->word)+1);
+	strcpy(buf, lp->word);
+	strcat(buf, rp->word);
+	v=newword(buf, tail);
+	efree(buf);
+	return v;
+}
+void Xconc(void){
+	word *lp=runq->argv->words;
+	word *rp=runq->argv->next->words;
+	word *vp=runq->argv->next->next->words;
+	int lc=count(lp), rc=count(rp);
+	if(lc!=0 || rc!=0){
+		if(lc==0 || rc==0){
+			Xerror1("null list in concatenation");
+			return;
+		}
+		if(lc!=1 && rc!=1 && lc!=rc){
+			Xerror1("mismatched list lengths in concatenation");
+			return;
+		}
+		vp=conclist(lp, rp, vp);
+	}
+	poplist();
+	poplist();
+	runq->argv->words=vp;
+}
+void Xassign(void){
+	var *v;
+	if(count(runq->argv->words)!=1){
+		Xerror1("variable name not singleton!");
+		return;
+	}
+	deglob(runq->argv->words->word);
+	v=vlook(runq->argv->words->word);
+	poplist();
+	globlist();
+	freewords(v->val);
+	v->val=runq->argv->words;
+	v->changed=1;
+	runq->argv->words=0;
+	poplist();
+}
+/*
+ * copy arglist a, adding the copy to the front of tail
+ */
+word *copywords(word *a, word *tail)
+{
+	word *v=0, **end;
+	for(end=&v;a;a=a->next,end=&(*end)->next)
+		*end=newword(a->word, 0);
+	*end=tail;
+	return v;
+}
+void Xdol(void){
+	word *a, *star;
+	char *s, *t;
+	int n;
+	if(count(runq->argv->words)!=1){
+		Xerror1("variable name not singleton!");
+		return;
+	}
+	s=runq->argv->words->word;
+	deglob(s);
+	n=0;
+	for(t=s;'0'<=*t && *t<='9';t++) n=n*10+*t-'0';
+	a=runq->argv->next->words;
+	if(n==0 || *t)
+		a=copywords(vlook(s)->val, a);
+	else{
+		star=vlook("*")->val;
+		if(star && 1<=n && n<=count(star)){
+			while(--n) star=star->next;
+			a=newword(star->word, a);
+		}
+	}
+	poplist();
+	runq->argv->words=a;
+}
+void Xqdol(void){
+	word *a, *p;
+	char *s;
+	int n;
+	if(count(runq->argv->words)!=1){
+		Xerror1("variable name not singleton!");
+		return;
+	}
+	s=runq->argv->words->word;
+	deglob(s);
+	a=vlook(s)->val;
+	poplist();
+	n=count(a);
+	if(n==0){
+		pushword("");
+		return;
+	}
+	for(p=a;p;p=p->next) n+=strlen(p->word);
+	s=emalloc(n);
+	if(a){
+		strcpy(s, a->word);
+		for(p=a->next;p;p=p->next){
+			strcat(s, " ");
+			strcat(s, p->word);
+		}
+	}
+	else
+		s[0]='\0';
+	pushword(s);
+	efree(s);
+}
+word *subwords(word *val, int len, word *sub, word *a)
+{
+	int n;
+	char *s;
+	if(!sub) return a;
+	a=subwords(val, len, sub->next, a);
+	s=sub->word;
+	deglob(s);
+	n=0;
+	while('0'<=*s && *s<='9') n=n*10+ *s++ -'0';
+	if(n<1 || len<n) return a;
+	for(;n!=1;--n) val=val->next;
+	return newword(val->word, a);
+}
+void Xsub(void){
+	word *a, *v;
+	char *s;
+	if(count(runq->argv->next->words)!=1){
+		Xerror1("variable name not singleton!");
+		return;
+	}
+	s=runq->argv->next->words->word;
+	deglob(s);
+	a=runq->argv->next->next->words;
+	v=vlook(s)->val;
+	a=subwords(v, count(v), runq->argv->words, a);
+	poplist();
+	poplist();
+	runq->argv->words=a;
+}
+void Xcount(void){
+	word *a;
+	char *s, *t;
+	int n;
+	char num[12];
+	if(count(runq->argv->words)!=1){
+		Xerror1("variable name not singleton!");
+		return;
+	}
+	s=runq->argv->words->word;
+	deglob(s);
+	n=0;
+	for(t=s;'0'<=*t && *t<='9';t++) n=n*10+*t-'0';
+	if(n==0 || *t){
+		a=vlook(s)->val;
+		itoa(num, count(a));
+	}
+	else{
+		a=vlook("*")->val;
+		itoa(num, a && 1<=n && n<=count(a)?1:0);
+	}
+	poplist();
+	pushword(num);
+}
+void Xlocal(void){
+	if(count(runq->argv->words)!=1){
+		Xerror1("variable name must be singleton\n");
+		return;
+	}
+	deglob(runq->argv->words->word);
+	runq->local=newvar(strdup(runq->argv->words->word), runq->local);
+	runq->local->val=copywords(runq->argv->next->words, (word *)0);
+	runq->local->changed=1;
+	poplist();
+	poplist();
+}
+void Xunlocal(void){
+	var *v=runq->local, *hid;
+	if(v==0) panic("Xunlocal: no locals!", 0);
+	runq->local=v->next;
+	hid=vlook(v->name);
+	hid->changed=1;
+	efree(v->name);
+	freewords(v->val);
+	efree((char *)v);
+}
+void freewords(word *w)
+{
+	word *nw;
+	while(w){
+		efree(w->word);
+		nw=w->next;
+		efree((char *)w);
+		w=nw;
+	}
+}
+void Xfn(void){
+	var *v;
+	word *a;
+	int end;
+	end=runq->code[runq->pc].i;
+	for(a=runq->argv->words;a;a=a->next){
+		v=gvlook(a->word);
+		if(v->fn) codefree(v->fn);
+		v->fn=codecopy(runq->code);
+		v->pc=runq->pc+2;
+		v->fnchanged=1;
+	}
+	runq->pc=end;
+	poplist();
+}
+void Xdelfn(void){
+	var *v;
+	word *a;
+	for(a=runq->argv->words;a;a=a->next){
+		v=gvlook(a->word);
+		if(v->fn) codefree(v->fn);
+		v->fn=0;
+		v->fnchanged=1;
+	}
+	poplist();
+}
+void Xpipe(void){
+	struct thread *p=runq;
+	int pc=p->pc, forkid;
+	int lfd=p->code[pc++].i;
+	int rfd=p->code[pc++].i;
+	int pfd[2];
+	if(pipe(pfd)<0){
+		Xerror("can't get pipe");
+		return;
+	}
+	switch(forkid=fork()){
+	case -1:
+		Xerror("try again");
+		break;
+	case 0:
+		start(p->code, pc+2, runq->local);
+		runq->ret=0;
+		close(pfd[PRD]);
+		pushredir(ROPEN, pfd[PWR], lfd);
+		break;
+	default:
+		start(p->code, p->code[pc].i, runq->local);
+		close(pfd[PWR]);
+		pushredir(ROPEN, pfd[PRD], rfd);
+		p->pc=p->code[pc+1].i;
+		p->pid=forkid;
+		break;
+	}
+}
+char *concstatus(char *s, char *t)
+{
+	static char v[NSTATUS+1];
+	int n=strlen(s);
+	strncpy(v, s, NSTATUS);
+	if(n<NSTATUS){
+		v[n]='|';
+		strncpy(v+n+1, t, NSTATUS-n-1);
+	}
+	v[NSTATUS]='\0';
+	return v;
+}
+void Xpipewait(void){
+	char status[NSTATUS+1];
+	if(runq->pid==-1)
+		setstatus(concstatus(runq->status, getstatus()));
+	else{
+		strncpy(status, getstatus(), NSTATUS);
+		status[NSTATUS]='\0';
+		Waitfor(runq->pid, 1);
+		runq->pid=-1;
+		setstatus(concstatus(getstatus(), status));
+	}
+}
+void Xrdcmds(void){
+	struct thread *p=runq;
+	word *prompt;
+	flush(err);
+	nerror=0;
+	if(flag['s'] && !truestatus())
+		pfmt(err, "status=%v\n", vlook("status")->val);
+	if(runq->iflag){
+		prompt=vlook("prompt")->val;
+		if(prompt)
+			promptstr=prompt->word;
+		else
+			promptstr="% ";
+	}
+	Noerror();
+	if(yyparse()){
+		if(!p->iflag || p->eof && !Eintr()){
+			if(p->cmdfile) efree(p->cmdfile);
+			closeio(p->cmdfd);
+			Xreturn();	/* should this be omitted? */
+		}
+		else{
+			if(Eintr()){
+				pchr(err, '\n');
+				p->eof=0;
+			}
+			--p->pc;	/* go back for next command */
+		}
+	}
+	else{
+		ntrap = 0;	/* avoid double-interrupts during blocked writes */
+		--p->pc;	/* re-execute Xrdcmds after codebuf runs */
+		start(codebuf, 1, runq->local);
+	}
+	freenodes();
+}
+void Xerror(char *s)
+{
+	if(strcmp(argv0, "rc")==0 || strcmp(argv0, "/bin/rc")==0)
+		pfmt(err, "rc: %s: %r\n", s);
+	else
+		pfmt(err, "rc (%s): %s: %r\n", argv0, s);
+	flush(err);
+	while(!runq->iflag) Xreturn();
+}
+void Xerror1(char *s)
+{
+	if(strcmp(argv0, "rc")==0 || strcmp(argv0, "/bin/rc")==0)
+		pfmt(err, "rc: %s\n", s);
+	else
+		pfmt(err, "rc (%s): %s\n", argv0, s);
+	flush(err);
+	while(!runq->iflag) Xreturn();
+}
+void Xbackq(void){
+	char wd[8193];
+	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;
+	}
+	switch(pid=fork()){
+	case -1: Xerror("try again");
+		close(pfd[PRD]);
+		close(pfd[PWR]);
+		return;
+	case 0:
+		close(pfd[PRD]);
+		start(runq->code, runq->pc+1, runq->local);
+		pushredir(ROPEN, pfd[PWR], 1);
+		return;
+	default:
+		close(pfd[PWR]);
+		f=openfd(pfd[PRD]);
+		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, 0);
+		/* 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=runq->code[runq->pc].i;
+		return;
+	}
+}
+/*
+ * Who should wait for the exit from the fork?
+ */
+void Xpipefd(void){
+	struct thread *p=runq;
+	int pc=p->pc;
+	char name[40];
+	int pfd[2];
+	int sidefd, mainfd;
+	if(pipe(pfd)<0){
+		Xerror("can't get pipe");
+		return;
+	}
+	if(p->code[pc].i==READ){
+		sidefd=pfd[PWR];
+		mainfd=pfd[PRD];
+	}
+	else{
+		sidefd=pfd[PRD];
+		mainfd=pfd[PWR];
+	}
+	switch(fork()){
+	case -1:
+		Xerror("try again");
+		break;
+	case 0:
+		start(p->code, pc+2, runq->local);
+		close(mainfd);
+		pushredir(ROPEN, sidefd, p->code[pc].i==READ?1:0);
+		runq->ret=0;
+		break;
+	default:
+		close(sidefd);
+		pushredir(ROPEN, mainfd, mainfd);	/* isn't this a noop? */
+		strcpy(name, Fdprefix);
+		itoa(name+strlen(name), mainfd);
+		pushword(name);
+		p->pc=p->code[pc+1].i;
+		break;
+	}
+}
+void Xsubshell(void){
+	int pid;
+	switch(pid=fork()){
+	case -1:
+		Xerror("try again");
+		break;
+	case 0:
+		start(runq->code, runq->pc+1, runq->local);
+		runq->ret=0;
+		break;
+	default:
+		Waitfor(pid, 1);
+		runq->pc=runq->code[runq->pc].i;
+		break;
+	}
+}
+void setstatus(char *s)
+{
+	setvar("status", newword(s, (word *)0));
+}
+char *getstatus(void){
+	var *status=vlook("status");
+	return status->val?status->val->word:"";
+}
+int truestatus(void){
+	char *s;
+	for(s=getstatus();*s;s++)
+		if(*s!='|' && *s!='0') return 0;
+	return 1;
+}
+void Xdelhere(void){
+	Unlink(runq->code[runq->pc++].s);
+}
+void Xfor(void){
+	if(runq->argv->words==0){
+		poplist();
+		runq->pc=runq->code[runq->pc].i;
+	}
+	else{
+		freelist(runq->local->val);
+		runq->local->val=runq->argv->words;
+		runq->local->changed=1;
+		runq->argv->words=runq->argv->words->next;
+		runq->local->val->next=0;
+		runq->pc++;
+	}
+}
+void Xglob(void){
+	globlist();
+}