从 $? [英] Extracting information from $?

问题描述

您能否就以下 perl 代码片段提供很好的解释.我从谷歌那里得到了一些想法，但仍然有很多基本的困惑.如果你能提供一些小笔记，很有帮助

Can you please provide good explanation about the following perl code snippet. I got some idea from google but still lots of basic confusion is there. great help if you can provide small notes on it

$exit_value  = $? >> 8;
$signal_num  = $? & 127;
$dumped_core = $? & 128;

推荐答案

引用 The Doc:

$?

最后一个管道关闭返回的状态，反引号(``)命令，成功调用 wait() 或 waitpid()，或从 system() 运算符调用.这只是传统Unix返回的16位状态字wait() 系统调用(或者看起来像它).就这样子进程的退出值真的是 ($?>> 8 )，而 $?&第127话哪个信号，如果有，该进程是从哪个信号中死亡的，以及 $?&128份报告是否有核心转储.

The status returned by the last pipe close, backtick (`` ) command, successful call to wait() or waitpid(), or from the system() operator. This is just the 16-bit status word returned by the traditional Unix wait() system call (or else is made up to look like it). Thus, the exit value of the subprocess is really ($?>> 8 ), and $? & 127 gives which signal, if any, the process died from, and $? & 128 reports whether there was a core dump.

<代码>>>8 给我们一个 16 位字的高字节.

>> 8 gives us the higher byte of a 16-bit word.

<代码>&127 本质上与 & 相同.0b01111111，给出该字的低 7 位部分.

& 127 is essentially the same as & 0b01111111, giving out the lower 7-bit part of that word.

<代码>&128 与 & 相同0b10000000，基本上就是检查结果的第8位.

& 128 is the same as & 0b10000000, which is basically checking for the 8th bit of the result.

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