diff --git a/sys/src/cmd/pstree.c b/sys/src/cmd/pstree.c
new file mode 100644
index 000000000..ecb992fb4
--- /dev/null
+++ b/sys/src/cmd/pstree.c
@@ -0,0 +1,189 @@
+#include <u.h>
+#include <libc.h>
+
+enum { NBUCKETS = 1024 };
+
+typedef struct Proc Proc;
+typedef struct Bucket Bucket;
+
+struct Proc {
+	int pid;
+	Proc *first, *last, *parent, *next;
+	Proc *bnext;
+};
+
+struct Bucket {
+	Proc *first, *last;
+} buck[NBUCKETS];
+
+Proc *
+getproc(int pid)
+{
+	Proc *p;
+	
+	for(p = buck[pid % NBUCKETS].first; p; p = p->next)
+		if(p->pid == pid)
+			return p;
+
+	return nil;
+}
+
+void
+addproc(int pid)
+{
+	Proc *p;
+	Bucket *b;
+	
+	p = mallocz(sizeof(*p), 1);
+	if(p == nil)
+		sysfatal("malloc: %r");
+	p->pid = pid;
+	b = buck + pid % NBUCKETS;
+	if(b->first != nil)
+		b->last->bnext = p;
+	else
+		b->first = p;
+	b->last = p;
+}
+
+int
+theppid(int pid)
+{
+	char *file;
+	int fd;
+	char buf[12];
+	int ppid;
+	
+	file = smprint("/proc/%d/ppid", pid);
+	fd = open(file, OREAD);
+	free(file);
+	if(fd < 0)
+		return 0;
+	ppid = 0;
+	if(read(fd, buf, sizeof buf) >= 0)
+		ppid = atoi(buf);
+	close(fd);
+	return ppid;
+}
+
+void
+addppid(int pid)
+{
+	int ppid;
+	Proc *p, *par;
+	
+	p = getproc(pid);
+	ppid = theppid(pid);
+	par = getproc(ppid);
+	if(par == nil)
+		par = getproc(0);
+	p->parent = par;
+	if(par->first != nil)
+		par->last->next = p;
+	else
+		par->first = p;
+	par->last = p;
+}
+
+void
+addprocs(void)
+{
+	int fd, rc, i;
+	Dir *d;
+	
+	fd = open("/proc", OREAD);
+	if(fd < 0)
+		sysfatal("open: %r");
+	rc = dirreadall(fd, &d);
+	if(rc < 0)
+		sysfatal("dirreadall: %r");
+	close(fd);
+	for(i = 0; i < rc; i++)
+		if(d[i].mode & DMDIR)
+			addproc(atoi(d[i].name));
+	for(i = 0; i < rc; i++)
+		if(d[i].mode & DMDIR)
+			addppid(atoi(d[i].name));
+	free(d);
+}
+
+Rune buf[512];
+
+int
+readout(char *file)
+{
+	int fd, rc, n;
+	char b[512];
+
+	fd = open(file, OREAD);
+	free(file);
+	if(fd < 0)
+		return -1;
+	n = 0;
+	while(rc = read(fd, b, 512), rc > 0) {
+		write(1, b, rc);
+		n += rc;
+	}
+	close(fd);
+	return n;
+}
+
+void
+printargs(int pid)
+{
+	char *file;
+	char b[28], *p;
+	int fd;
+
+	if(pid == 0)
+		return;
+	if(readout(smprint("/proc/%d/args", pid)) > 0)
+		return;
+	file = smprint("/proc/%d/status", pid);
+	fd = open(file, OREAD);
+	free(file);
+	if(fd < 0)
+		return;
+	memset(b, 0, sizeof b);
+	if(read(fd, b, 27) <= 0)
+		return;
+	p = b + strlen(b) - 1;
+	while(*p == ' ')
+		*p-- = 0;
+	print("%s", b);
+}
+
+void
+descend(Proc *p, Rune *r)
+{
+	Rune last;
+	Proc *q;
+	
+	last = *--r;
+	*r = last == L' ' ? L'└' : L'├';
+	print("%S", buf);
+	printargs(p->pid);
+	print(" [%d]\n", p->pid);
+	*r = last;
+	*++r = L'│';
+	for(q = p->first; q; q = q->next) {
+		if(q->next == nil)
+			*r = L' ';
+		descend(q, r + 1);
+	}
+	*r = 0;
+}
+
+void
+printprocs(void)
+{
+	descend(getproc(0), buf);
+}
+
+void
+main()
+{
+	addproc(0);
+	addprocs();
+	printprocs();
+}