如何获取充当 stdin/stdout 的文件的名称？

发布于 2024-10-31 13:39:50 字数 354 浏览 3 评论 0原文

我遇到以下问题。我想用 Fortran90 编写一个程序，我希望能够像这样调用：

./program.x < main.in > main.out

除了“main.out”（我可以在调用程序时设置其名称）之外，还必须编写辅助输出，我希望它们具有与“main.in”或“main.out”类似的名称（它们实际上并不称为“main”）；但是，当我使用：

INQUIRE(UNIT=5,NAME=sInputName)

sInputName 的内容变为“Stdin”而不是文件名。有没有办法在调用程序时获取链接到 stdin/stdout 的文件名？

原文

I'm having the following problem. I want to write a program in Fortran90 which I want to be able to call like this:

./program.x < main.in > main.out

Additionally to "main.out" (whose name I can set when calling the program), secondary outputs have to be written and I wanted them to have a similar name to either "main.in" or "main.out" (they are not actually called "main"); however, when I use:

INQUIRE(UNIT=5,NAME=sInputName)

The content of sInputName becomes "Stdin" instead of the name of the file. Is there some way to obtain the name of files that are linked to stdin/stdout when the program is called??

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妥活 2024-11-07 13:39:50

不幸的是，I/O 重定向的要点是您的程序不必知道输入/输出文件是什么。在基于 UNIX 的系统上，您无法将命令行参数视为 <; main.in > main.out 实际上是由 shell 处理的，shell 在调用程序之前使用这些文件来设置标准输入和输出。

您必须记住，有时标准输入和输出甚至不是文件，因为它们可能是终端或管道。例如，

./generate_input | ./program.x | less

因此一种解决方案是重新设计程序，使输出文件成为显式参数。

./program.x --out=main.out

这样你的程序就知道文件名。代价是您的程序现在负责打开（并且可能创建）文件。

也就是说，在 Linux 系统上，您实际上可以找到标准文件句柄从特殊的 /proc 文件系统指向的位置。每个文件描述符都会有符号链接

/proc/<process_id>/fd/0 -> standard_input
/proc/<process_id>/fd/1 -> standard_output
/proc/<process_id>/fd/2 -> standard_error

抱歉，我不懂 fortran，但检查输出文件的伪代码方式可能是：

out_name = realLink( "/proc/"+getpid()+"/fd/1" )
if( isNormalFile( out_name ) )
    ...

记住我之前所说的，没有保证这实际上是一个正常文件。它可以是一个终端设备，一个管道，一个网络套接字，等等......另外，我不知道除了 redhat/centos linux 之外，它还可以在哪些其他操作系统上运行，所以它可能不那么便携。更多的是一种诊断工具。

Unfortunately the point of i/o redirection is that you're program doesn't have to know what the input/output files are. On unix based systems you cannot look at the command line arguments as the < main.in > main.out are actually processed by the shell which uses these files to set up standard input and output before your program is invoked.

You have to remember that sometimes the standard input and output will not even be files, as they could be a terminal or a pipe. e.g.

./generate_input | ./program.x | less

So one solution is to redesign your program so that the output file is an explicit argument.

./program.x --out=main.out

That way your program knows the filename. The cost is that your program is now responsible for openning (and maybe creating) the file.

That said, on linux systems you can actually find yout where your standard file handles are pointing from the special /proc filesystem. There will be symbolic links in place for each file descriptor

/proc/<process_id>/fd/0 -> standard_input
/proc/<process_id>/fd/1 -> standard_output
/proc/<process_id>/fd/2 -> standard_error

Sorry, I don't know fortran, but a psudeo code way of checking the output file could be:

out_name = realLink( "/proc/"+getpid()+"/fd/1" )
if( isNormalFile( out_name ) )
    ...

Keep in mind what I said earlier, there is no garauntee this will actually be a normal file. It could be a terminal device, a pipe, a network socket, whatever... Also, I do not know what other operating systems this works on other than redhat/centos linux, so it may not be that portable. More a diagnostic tool.

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