116 #ifdef FORK
117 pid = FORK ();
118 #else
119 pid = __fork ();
120 #endif
121 if(pid == (pid_t) 0)
122 {
123 /** Child side. */
124 constchar*new_argv[4];
125 new_argv[0] = SHELL_NAME;
126 new_argv[1] = "-c";
127 new_argv[2] = line;
128 new_argv[3] = NULL;
129
130 /** Restore the signals. */
131 (void) __sigaction (SIGINT, &intr, (structsigaction *) NULL);
132 (void) __sigaction (SIGQUIT, &quit, (structsigaction *) NULL);
133 (void) __sigprocmask (SIG_SETMASK, &omask, (sigset_t *) NULL);
134 INIT_LOCK ();
135
136 /** Exec the shell. */
137 (void) __execve (SHELL_PATH, (char*const*) new_argv, __environ); //exec被代替改程序，如果失败的话，就是执行下一条
138 _exit (127); //直接进入内核中断，返回127.
139 }
140 elseif(pid < (pid_t) 0)
141 /** The fork failed. */
142 status = -1;
143 else
144 /** Parent side. */
145 {
146 /** Note the system() is a cancellation point. But since we call
147 waitpid() which itself is a cancellation point we do not
148 have to do anything here. */
149 if(TEMP_FAILURE_RETRY (__waitpid (pid, &status, 0)) != pid)
150 status = -1;
151 }