bash 如何查找 Linux 命令行实用程序的退出代码的含义？
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How to lookup the meaning of exit codes for Linux command line utilities?
提问by chrm
I have my prompt (bash) configured to print out the exit code from the last command, if it wasn't successful (aka not zero). Therefore I'm seeing a lot of exit codes, even when a program seems to encounter no problems. Is there a way to lookup the meaning of these exit codes?
我的提示 (bash) 被配置为打印出最后一个命令的退出代码，如果它不成功（也就是非零）。因此，我看到了很多退出代码，即使程序似乎没有遇到任何问题。有没有办法查找这些退出代码的含义？
I always try the man pages, info pages or the "--help" option, but to no avail.
我总是尝试使用手册页、信息页或“--help”选项，但无济于事。
To clarify, I'm asking about the utilities that come with Linux, like cd, ls, du, ...
为了澄清起见，我问的是 Linux 附带的实用程序，例如cd, ls, du, ...
回答by Jonathan Leffler
There isn't a standardized meaning for the exit codes of programs beyond '0 is OK; anything else means something went wrong'. And strictly, that applies to C and C++ only - there, exit(0);or exit(EXIT_SUCCESS);both exit with success, but the value returned to the O/S might be different.
程序的退出代码超过'0就可以了，没有一个标准化的含义；其他任何事情都意味着出了问题'。严格来说，这仅适用于 C 和 C++ - 在那里，exit(0);或exit(EXIT_SUCCESS);两者都成功退出，但返回给 O/S 的值可能不同。
There are exceptions to even the zero-on-success rule. Obviously, there are careless programs that don't return a defined exit status; such programs are best avoided. There are other not quite so careless programs that always return 0, even when something went wrong; they too are often best avoided.
即使是成功为零的规则也有例外。显然，有些粗心的程序不会返回定义的退出状态；最好避免此类程序。还有其他不太粗心的程序，即使出现问题，也总是返回 0；他们也往往最好避免。
However, there are also programs that carefully encode quite a lot of information into the exit status, and simply getting a non-zero exit status does not mean such programs failed. Of course, the programs document the meanings of the exit statuses.
但是，也有一些程序会仔细地将相当多的信息编码到退出状态中，并且仅仅获得非零退出状态并不意味着此类程序失败。当然，程序记录了退出状态的含义。
POSIX is careful to document exit statuses for programs.
POSIX 小心地记录程序的退出状态。
The manual pages for a program should document the exit statuses. On Unix, if there is no such documentation, then assume zero-on-success and anything else is a failure.
程序的手册页应该记录退出状态。在 Unix 上，如果没有这样的文档，那么假设成功为零，其他任何事情都是失败的。
Note that if bashfails to execute a command, it will return stylized statuses:
请注意，如果bash无法执行命令，它将返回样式化状态：
- 127 if the file does not exist or cannot be found
- 126 if you do not have execute permission on the file
- 127 如果文件不存在或找不到
- 126 如果您没有对该文件的执行权限
Also, if the program dies because of a signal, bashlets you know by encoding the exit status as:
此外，如果程序因信号而bash终止，请通过将退出状态编码为：
128 + signal-number
128 + signal-number
Hence SIGHUP yields 129, SIGILL yields 132, SIGTERM yields 143, etc. However, it is possible for a program to exit with any of those statuses and mean something different from what bashmeans. That said, it is a relatively unusual program that exits with any of those exit statuses, so you're usually safe.
因此，SIGHUP 产生 129，SIGILL 产生 132，SIGTERM 产生 143，等等。但是，程序有可能以任何这些状态退出并且意味着与 what mean 不同的bash含义。也就是说，这是一个相对不寻常的程序，它以任何这些退出状态退出，因此您通常是安全的。
Note that different operating systems have different conventions: Unix provides an 8-bit status with zero for success; Windows provides a much larger range for the exit status values (16-bits or 32-bits); VMS used zero to mean failure, I believe.
请注意，不同的操作系统有不同的约定：Unix 提供 8 位状态，成功为零；Windows 为退出状态值提供了更大的范围（16 位或 32 位）；我相信，VMS 使用零表示失败。
回答by tripleee
The man pages are the conventional place for this documentation. If you are on e.g. Debian, you would even be expected to file a bug report against utilities which have undocumented exit codes.
手册页是本文档的常规位置。如果您使用例如 Debian，您甚至需要针对具有未记录退出代码的实用程序提交错误报告。
回答by Ken
The advanced Bash scripting guide also provides exit codes with special meanings.
高级 Bash 脚本指南还提供了具有特殊含义的退出代码。
