shell can launch another user processgit add .git add .!

rocklibc/include/syscall.h

@@ -13,7 +13,8 @@
 #define SYS_FORK    21
 #define SYS_EXEC    22
 #define SYS_DUP2    23
-#define SYS_LSEEK    24
+#define SYS_LSEEK   24
+#define SYS_WAIT    25
 
 int open(const char* path);
 int write(int fd, const void *buf, size_t count);
@@ -32,5 +33,6 @@ int pty(int* slave);
 int fork();
 int exec(const char* path);
 int dup2(int src, int dst);
+int waitpid(int pid, int* status);
 
 #endif