diff --git a/labs/03_shlab/tsh.c b/labs/03_shlab/tsh.c
index 8b986a8..99b3201 100644
--- a/labs/03_shlab/tsh.c
+++ b/labs/03_shlab/tsh.c
@@ -1,8 +1,8 @@
 /*
  * tsh - A tiny shell program with job control
  *
- * Name: <fill in>
- * Student id: <fill in>
+ * Name: Hajin Ju
+ * Student id: 2024062806
  */
 #include <ctype.h>
 #include <errno.h>
@@ -169,13 +169,21 @@ int main(int argc, char **argv) {
  */
 void eval(char *cmdline) {
     pid_t pid;
+
+    sigset_t mask, prev_mask;
+
     char *argv[MAXARGS];
 
     int bg = parseline(cmdline, argv);
 
     if (argv[0] && !builtin_cmd(argv)) {
+        sigemptyset(&mask);
+        sigaddset(&mask, SIGCHLD);
+        sigprocmask(SIG_BLOCK, &mask, &prev_mask);
+
         if ((pid = fork()) == 0) {// Child process
-            setpgid(0, 0);        // Set new process group
+            sigprocmask(SIG_SETMASK, &prev_mask, NULL);
+            setpgid(0, 0);// Set new process group
 
             if (execve(argv[0], argv, environ) < 0) {
                 printf("%s: Command not found\n", argv[0]);
@@ -185,11 +193,14 @@ void eval(char *cmdline) {
 
         if (!bg) {// Foreground job
             addjob(jobs, pid, FG, cmdline);
-            waitfg(pid);
+
         } else {// Background job
             addjob(jobs, pid, BG, cmdline);
             fprintf(stderr, "[%d] (%d) %s", pid2jid(pid), pid, cmdline);
         }
+        sigprocmask(SIG_SETMASK, &prev_mask, NULL);
+
+        if (!bg) waitfg(pid);
     }
 }
 
@@ -271,8 +282,8 @@ int builtin_cmd(char **argv) {
  */
 void do_bgfg(char **argv) {
     struct job_t *job = NULL;
-    pid_t pid;
-    int jid;
+    pid_t pid = 0;
+    int jid = 0;
 
     if (argv[1] == NULL) {
         printf("%s command requires PID or %%jobid argument\n", argv[0]);
@@ -354,7 +365,7 @@ void sigchld_handler(int sig) {
         } else if (WIFSTOPPED(status)) {
             struct job_t *job = getjobpid(jobs, pid);
             if (job != NULL) {
-				job->state = ST;
+                job->state = ST;
                 fprintf(stderr, "Job [%d] (%d) stopped by signal %d\n", job->jid, pid, WSTOPSIG(status));
             }
         }