should be finished

shell.c

@@ -88,42 +88,6 @@ void parse(char* line, command_t* p_cmd) {
     }
 }
 
-/**
- * Determines if the executable in p_cmd (i.e., p_cmd->argv[0]) can be found
- * in one of the directories in $PATH. Returns true if so, else false.
- * If the executable is found in $PATH, then p_cmd->argv[0] is mutated to be
- * the absolute path of the executable.
- *
- * To see the format of $PATH, run `echo $PATH` in your terminal, which should
- * output something like
- * /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/mnt/learncli/bin
- *
- * For example, suppose the executable is "ls". This function needs to find its
- * absolute path in the file system. For the $PATH above,
- * it appends "/ls" to the first directory, resulting in
- * /usr/local/sbin/ls. However, this file does not exist, and same for the next
- * two directories. However, /usr/bin/ls exists, so p_cmd->argv[0] is set to
- * "/usr/bin/ls", and the function returns true.
- *
- * If the executable is "doesnotexist", then this function would not find that
- * file after checking all directories in $PATH, so it would return false.
- *
- * Note: This behaves similarly to the `which` command, e.g., `which ls`.
- *
- * To access $PATH within C, use getenv.
- * For example, char* path = getenv("PATH");
- *
- * To parse PATH, we recommend strtok, as described in the docstring for the
- * parse function.
- *
- * To check if a file exists, use access with amode F_OK
- * (https://pubs.opengroup.org/onlinepubs/009695299/functions/access.html).
- *
- * @param p_cmd
- * @return true (if command in PATH) | false (if command not in PATH). Remember
- * to mutate p_cmd->argv[0] to be the full path of the executable if it is in
- * PATH
- */
 bool find_full_path(command_t* p_cmd) {
     char* path_tokens = strtok(getenv("PATH"), ":");
 
@@ -147,8 +111,31 @@ bool find_full_path(command_t* p_cmd) {
 }
 
 int execute(command_t* p_cmd) {
-    // TODO:
-    return 0;
+    if (is_builtin(p_cmd)) {
+        return do_builtin(p_cmd);
+    }
+
+    if (!find_full_path(p_cmd)) {
+        printf("Command %s not found!\n", p_cmd->argv[0]);
+        return ERROR;
+    }
+
+    // start fork
+    pid_t pid = fork();
+
+    if (pid < 0) {
+        return ERROR;
+    } else if (pid == 0) {
+        // child process
+        execv(p_cmd->argv[0], p_cmd->argv);
+        exit(EXIT_FAILURE);
+    } else {
+        // parent process
+        int status;
+        waitpid(pid, &status, 0);
+    }
+
+    return SUCCESS;
 }
 
 bool is_builtin(command_t* p_cmd) {