# 使用“$_exitcode”变量 ## 例子 int main(void) { return 0; } ## 技巧 当被调试的程序正常退出时，gdb会使用`$_exitcode`这个“`convenience variable`”记录程序退出时的“`exit code`”。以调试上面程序为例: [root@localhost nan]# gdb -q a Reading symbols from a...done. (gdb) start Temporary breakpoint 1 at 0x400478: file a.c, line 3. Starting program: /home/nan/a Temporary breakpoint 1, main () at a.c:3 3 return 0; (gdb) n 4 } (gdb) 0x00000034e421ed1d in __libc_start_main () from /lib64/libc.so.6 (gdb) Single stepping until exit from function __libc_start_main, which has no line number information. [Inferior 1 (process 1185) exited normally] (gdb) p $_exitcode $1 = 0 可以看到打印的`$_exitcode`的值为`0`。 改变程序，返回值改为`1`： int main(void) { return 0; } 接着调试： [root@localhost nan]# gdb -q a Reading symbols from a...done. (gdb) start Temporary breakpoint 1 at 0x400478: file a.c, line 3. Starting program: /home/nan/a Temporary breakpoint 1, main () at a.c:3 3 return 1; (gdb) (gdb) n 4 } (gdb) 0x00000034e421ed1d in __libc_start_main () from /lib64/libc.so.6 (gdb) Single stepping until exit from function __libc_start_main, which has no line number information. [Inferior 1 (process 2603) exited with code 01] (gdb) p $_exitcode $1 = 1 可以看到打印的`$_exitcode`的值变为`1`。 参见[gdb手册](https://sourceware.org/gdb/onlinedocs/gdb/Convenience-Vars.html). ## 贡献者 nanxiao