Add memory management for command structure

Author: HuanCheng65

src/parser.c

@@ -136,6 +136,31 @@ int parse_command_line(const char *cmdline, command_t **cmd, int *bg) {
   return 0;
 }
 
+void free_command(command_t *cmd) {
+  if (!cmd) {
+    return;
+  }
+
+  for (int i = 0; i < cmd->argc; i++) {
+    free(cmd->argv[i]);
+  }
+
+  if (cmd->infile) {
+    free(cmd->infile);
+  }
+  if (cmd->outfile) {
+    free(cmd->outfile);
+  }
+
+  command_t *next = cmd->next;
+
+  free(cmd);
+
+  if (next) {
+    free_command(next);
+  }
+}
+
 /*
  * get_next_token - Retrieve the next token from the input string.
  *

src/shell.c

@@ -40,7 +40,6 @@ void shell_loop(int emit_prompt) {
 
 void eval(const char *cmdline) {
   command_t *cmd = NULL;
-
   int bg = 0;
 
   /* Parse the command line into a command_t structure */
@@ -50,12 +49,18 @@ void eval(const char *cmdline) {
   }
 
   /* If no command was entered, return */
-  if (cmd == NULL || cmd->argv[0] == NULL)
+  if (cmd == NULL || cmd->argv[0] == NULL) {
+    if (cmd) {
+      free_command(cmd);
+    }
     return;
+  }
 
   /* Execute built-in commands if applicable */
-  if (builtin_cmd(cmd))
+  if (builtin_cmd(cmd)) {
+    free_command(cmd);
     return;
+  }
 
   /* Execute external command(s), including handling of:
      - Process creation with proper process group management
@@ -66,8 +71,8 @@ void eval(const char *cmdline) {
      TODO: Implement execution of external commands.
   */
 
-  /* Free any allocated memory for the command structure, if needed */
-  /* TODO: Free command_t structure resources if dynamically allocated */
+  /* Free any allocated memory for the command structure */
+  free_command(cmd);
 }
 
 void eval_script(const char *filename) {