高手请进，gdb管道命令后自动退出

[heronism]

centos 6.5系统，执行echo "bt"|gdb --quiet -nx /proc/10214/exe 16691后，打印出bt命令的结果后自动quit。如下：

warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
0x0ffd6cf4 in read () from /lib/libpthread.so.0
(gdb) #0  0x0ffd6cf4 in read () from /lib/libpthread.so.0
#1  0x0fe6fd58 in rl_getc () from /lib/libreadline.so.6
#2  0x0fe6fc9c in rl_read_key () from /lib/libreadline.so.6
#3  0x0fe4b3f8 in readline_internal_char () from /lib/libreadline.so.6
#4  0x0fe4b5c8 in ?? () from /lib/libreadline.so.6
#5  0x0fe4b61c in ?? () from /lib/libreadline.so.6
#6  0x0fe4ae3c in readline () from /lib/libreadline.so.6
#7  0x10546bbc in main_read (procName=0xbfb99eb0 "./app") at ../source/test_common_shell.c:773
#8  0x105c1898 in app_main (argc=2, argv=0xbfb99c34) at ../source/test_win_entry.c:289
#9  0x1054ba00 in main (argc=2, argv=0xbfb99c34) at ../source/test_common_watchdog.c:873
(gdb) quit
A debugging session is active.

        Inferior 1 [process 1973] will be detached.

Quit anyway? (y or n) [answered Y; input not from terminal]
Detaching from program: /proc/1973/exe, process 1973

我的问题是，按照管道的理解不是应该只输出bt的打印，后面的quit和y的输入管道里明明没有啊，是哪个环节输入给gdb的呢（看样子应该是gdb自己），这里面的原理是什么，请高手帮忙分析下，谢谢

[heronism]

呼唤高手，结贴给分。