diff -r e08745605692 sys/include/thread.h
--- a/sys/include/thread.h	Mon Nov 14 00:00:00 2011 +0100
+++ b/sys/include/thread.h	Sun Nov 20 00:00:00 2011 +0100
@@ -98,6 +98,8 @@
 void	threadkillgrp(int);	/* kill threads in group */
 void	threadmain(int argc, char *argv[]);
 void	threadnonotes(void);
+int	threadspawn(int[3], char*, char*[]);
+int	threadspawnl(int[3], char*, ...);
 int	threadnotify(int (*f)(void*, char*), int in);
 int	threadid(void);
 int	threadpid(int);
diff -r e08745605692 sys/man/2/thread
--- a/sys/man/2/thread	Mon Nov 14 00:00:00 2011 +0100
+++ b/sys/man/2/thread	Sun Nov 20 00:00:00 2011 +0100
@@ -41,6 +41,8 @@
 threadpid,
 threadsetgrp,
 threadsetname,
+threadspawn,
+threadspawnl,
 threadwaitchan,
 yield \- thread and proc management
 .SH SYNOPSIS
@@ -128,6 +130,8 @@
 int	chanclose(Channel *c);
 int	chanclosing(Channel *c);
 .XX
+int	threadspawnl(int fd[3], char *file, ...)
+int	threadspawn(int fd[3], char *file, char *args[])
 void	procexecl(Channel *cpid, char *file, ...)
 void	procexec(Channel *cpid, char *file, char *args[])
 Channel*	threadwaitchan(void)
@@ -237,6 +241,7 @@
 .IR procexec ,
 .IR procexecl ,
 .IR threadexits ,
+.IR threadspawn ,
 .IR alt ,
 .IR send ,
 and
@@ -362,6 +367,17 @@
 .I procexec(l)
 mount pipes there.
 .PP
+.I Threadspawnl
+and
+.I threadspawn
+are like
+.I threadexecl
+and
+.I threadexec
+but do not replace the current thread.
+They return the pid of the invoked program on success, or
+\-1 on error.
+.PP
 .I Threadwaitchan
 returns a channel of pointers to
 .B Waitmsg
diff -r e08745605692 sys/src/libthread/exec.c
--- a/sys/src/libthread/exec.c	Mon Nov 14 00:00:00 2011 +0100
+++ b/sys/src/libthread/exec.c	Sun Nov 20 00:00:00 2011 +0100
@@ -78,3 +78,63 @@
 	procexec(pidc, f, &f+1);
 }
 
+static void
+execproc(void *v)
+{
+	Execjob *e;
+
+	e = v;
+	rfork(RFFDG);
+	dup(e->fd[0], 0);
+	dup(e->fd[1], 1);
+	dup(e->fd[2], 2);
+	procexec(e->c, e->cmd, e->argv);
+	threadexits(nil);
+}
+
+int
+threadspawn(int fd[3], char *cmd, char *argv[])
+{
+	int pid;
+	Execjob e;
+
+	e.fd = fd;
+	e.cmd = cmd;
+	e.argv = argv;
+	e.c = chancreate(sizeof(void*), 0);
+	proccreate(execproc, &e, 65536);
+	close(fd[0]);
+	close(fd[1]);
+	close(fd[2]);
+	pid = recvul(e.c);
+	chanfree(e.c);
+	return pid;
+}
+
+int
+threadspawnl(int fd[3], char *cmd, ...)
+{
+	char **argv, *s;
+	int n, pid;
+	va_list arg;
+
+	va_start(arg, cmd);
+	for(n=0; va_arg(arg, char*) != nil; n++)
+		;
+	n++;
+	va_end(arg);
+
+	argv = malloc(n*sizeof(argv[0]));
+	if(argv == nil)
+		return -1;
+
+	va_start(arg, cmd);
+	for(n=0; (s=va_arg(arg, char*)) != nil; n++)
+		argv[n] = s;
+	argv[n] = 0;
+	va_end(arg);
+
+	pid = threadspawn(fd, cmd, argv);
+	free(argv);
+	return pid;
+}
diff -r e08745605692 sys/src/libthread/threadimpl.h
--- a/sys/src/libthread/threadimpl.h	Mon Nov 14 00:00:00 2011 +0100
+++ b/sys/src/libthread/threadimpl.h	Sun Nov 20 00:00:00 2011 +0100
@@ -24,6 +24,7 @@
 typedef struct Tqueue	Tqueue;
 typedef struct Thread	Thread;
 typedef struct Execargs	Execargs;
+typedef struct Execjob	Execjob;
 typedef struct Proc		Proc;
 
 /* must match list in sched.c */
@@ -101,6 +102,14 @@
 	int		fd[2];
 };
 
+struct Execjob
+{
+	int *fd;
+	char *cmd;
+	char **argv;
+	Channel *c;
+};
+
 struct Proc
 {
 	Lock		lock;