如何在 Fortran 中使用命令行参数? [英] How to use command line arguments in Fortran?

问题描述

海湾合作委员会 4.6 版

GCC version 4.6

问题:要找到一种方法将参数输入到可执行文件中，例如 a.out，从命令行输入 - 更具体地说，输入一个双精度数组精确数字.

The Problem: To find a way to feed in parameters to the executable, say a.out, from the command line - more specifically feed in an array of double precision numbers.

尝试: 使用 READ(*,*) 命令，该命令在标准中较旧:程序 test.f -

Attempt: Using the READ(*,*) command, which is older in the standard: Program test.f -

PROGRAM MAIN  
     REAL(8)    :: A,B  
     READ(*,*) A,B
     PRINT*, A+B, COMMAND_ARGUMENT_COUNT()
END PROGRAM MAIN

执行 -

$ gfortran test.f
$ ./a.out 3.D0 1.D0

这没有用.一番反省，发现

This did not work. On a bit of soul-searching, found that

$./a.out
3.d0,1.d0
   4.0000000000000000                0

确实可以，但是第二行是输入提示，没有达到单行完成的目的.此外，COMMAND_ARGUMENT_COUNT() 显示，输入到输入提示中的数字并不真正算作命令行参数"，这与 PERL 不同.

does work, but the second line is an input prompt, and the objective of getting this done in one-line is not achieved. Also the COMMAND_ARGUMENT_COUNT() shows that the numbers fed into the input prompt don't really count as 'command line arguments', unlike PERL.

推荐答案

如果您想在命令行上将参数提供给您的程序，请使用(自 Fortran 2003 起)标准内在子例程 GET_COMMAND_ARGUMENT.这样的事情可能会奏效

If you want to get the arguments fed to your program on the command line, use the (since Fortran 2003) standard intrinsic subroutine GET_COMMAND_ARGUMENT. Something like this might work

PROGRAM MAIN  
     REAL(8)    :: A,B
     integer :: num_args, ix
     character(len=12), dimension(:), allocatable :: args

     num_args = command_argument_count()
     allocate(args(num_args))  ! I've omitted checking the return status of the allocation 

     do ix = 1, num_args
         call get_command_argument(ix,args(ix))
         ! now parse the argument as you wish
     end do

     PRINT*, A+B, COMMAND_ARGUMENT_COUNT()
END PROGRAM MAIN

注意:

• 子例程 get_command_argument 的第二个参数是一个字符变量，您必须将其解析为真实的(或其他).另请注意，我只允许 args 数组的每个元素中包含 12 个字符，您可能想要摆弄这个.
• 正如您已经发现的那样，read 不用于读取 Fortran 程序中的命令行参数.

• The second argument to the subroutine get_command_argument is a character variable which you'll have to parse to turn into a real (or whatever). Note also that I've allowed only 12 characters in each element of the args array, you may want to fiddle around with that.
• As you've already figured out read isn't used for reading command line arguments in Fortran programs.

由于您想读取实数数组，因此最好使用您已经想到的方法，即在程序启动后从终端读取它们，这取决于您.

Since you want to read an array of real numbers, you might be better off using the approach you've already figured out, that is reading them from the terminal after the program has started, it's up to you.

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