diff --git a/Makefile b/Makefile
index 09d790c..9ace969 100644
--- a/Makefile
+++ b/Makefile
@@ -181,6 +181,7 @@ UPROGS=\
 	_usertests\
 	_wc\
 	_zombie\
+	_test_fork
 
 fs.img: mkfs README $(UPROGS)
 	./mkfs fs.img README $(UPROGS)
diff --git a/proc.c b/proc.c
index 74657fc..fd82a0b 100644
--- a/proc.c
+++ b/proc.c
@@ -545,3 +545,18 @@ procdump(void)
     cprintf("\n");
   }
 }
+
+int sys_nb_children() {
+  int n = 0;
+  struct proc *p = 0;
+  acquire(&ptable.lock);
+  for(p = ptable.proc; p < &ptable.proc[NPROC]; p++){
+    if(p->state == UNUSED)
+      continue;
+    if(p->parent == myproc())
+      n++;
+  }  
+  release(&ptable.lock);
+
+  return n;
+}
diff --git a/syscall.c b/syscall.c
index ee85261..115488b 100644
--- a/syscall.c
+++ b/syscall.c
@@ -103,6 +103,7 @@ extern int sys_unlink(void);
 extern int sys_wait(void);
 extern int sys_write(void);
 extern int sys_uptime(void);
+extern int sys_nb_children(void);
 
 static int (*syscalls[])(void) = {
 [SYS_fork]    sys_fork,
@@ -126,6 +127,7 @@ static int (*syscalls[])(void) = {
 [SYS_link]    sys_link,
 [SYS_mkdir]   sys_mkdir,
 [SYS_close]   sys_close,
+[SYS_nb_children]   sys_nb_children,
 };
 
 void
diff --git a/syscall.h b/syscall.h
index 33d0377..fb4e3e7 100644
--- a/syscall.h
+++ b/syscall.h
@@ -22,3 +22,4 @@
 #define SYS_link   19
 #define SYS_mkdir  20
 #define SYS_close  21
+#define SYS_nb_children 22
diff --git a/test_fork.c b/test_fork.c
new file mode 100644
index 0000000..7ed7281
--- /dev/null
+++ b/test_fork.c
@@ -0,0 +1,16 @@
+#include "types.h"
+#include "user.h"
+
+int main() {
+  for(int i = 0; i< 4; i++) {
+    if(fork() == 0) break;
+  }
+  
+  printf(1, "%d - %d children\n", getpid(), nb_children());
+  sleep(1);
+
+  for(int i = 0; i<4; i++)
+    wait();
+
+  exit();
+}
diff --git a/user.h b/user.h
index e48c7f7..7166ad7 100644
--- a/user.h
+++ b/user.h
@@ -25,6 +25,7 @@ int getpid(void);
 char* sbrk(int);
 int sleep(int);
 int uptime(void);
+int nb_children();
 
 // ulib.c
 int stat(const char*, struct stat*);
diff --git a/usys.S b/usys.S
index 8bfd8a1..347d725 100644
--- a/usys.S
+++ b/usys.S
@@ -29,3 +29,4 @@ SYSCALL(getpid)
 SYSCALL(sbrk)
 SYSCALL(sleep)
 SYSCALL(uptime)
+SYSCALL(nb_children)