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I have a Fortran executable that takes a couple keyboard inputs before doing a calculation. It works in the terminal entering the inputs, but I want to using piping to enter the inputs (Windows 10 command line). When I only have one keyboard input, the piping works perfectly. How can I get it to work with multiple inputs?

I can almost get it to work based on a similar question here: Passing arguments to interactive fortran program. I reviewed documentation on standard inputs, but I still can't figure it out.

Here is an example Fortran program with only one input, and it works with piping.

 program foo integer n character*80 c write (*,*) 'Enter 1,2,3 for cat,dog,fish' read (*,*) n if (n .eq. 1) then write (*,*) 'meow' elseif (n .eq. 2) then write (*,*) 'woof' elseif (n .eq. 3) then write (*,*) 'blurp' else write (*,*) 'error1' endif C write (*,*) 'Enter y,n for yay,nay' C read (*,*) c C if (c == 'y') then C write (*,*) 'yes' C elseif (c == 'n') then C write (*,*) 'no' C elseif (n .eq. 3) then C else C write (*,*) 'error2' C endif end

Terminal test:

C:\my\file\path> C:\my\file\path\foo.exe Enter 1,2,3 for cat,dog,fish 2 woof C:\my\file\path> echo 1 | C:\my\file\path\foo.exe Enter 1,2,3 for cat,dog,fish meow

Here is an example Fortran program with multiple inputs, and it doesn't work with piping.

Same program as above, but commented lines are uncommented. Terminal test:

C:\my\file\path> C:\my\file\path\foo.exe Enter 1,2,3 for cat,dog,fish 3 blurp Enter y,n for yay,nay n no C:\my\file\path> echo 1 y | C:\my\file\path\foo.exe Enter 1,2,3 for cat,dog,fish meow Enter y,n for yay,nay At line 18 of file C:/my/file/path/foo.f (unit = 5, file = 'stdin') Fortran runtime error: End of file Error termination. Backtrace: Could not print backtrace: libbacktrace could not find executable to open #0 0x318dd91b #1 0x318d6b34 #2 0x318d355b #3 0x318d7f6c #4 0x318e8e9d #5 0x318d88df #6 0x318d5190 #7 0x318b1691 #8 0x318f3f93 #9 0x318b13c0 #10 0x318b14f5 #11 0xb9677c23 #12 0xba24d4d0 #13 0xffffffff

Compiler information: GNU gfortran, CMake based off wiki example

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    The answer to this depends on how the program works. If it does not have command line parameters or does not take stdin, then it will not work as a "one-liner". There might be some "record and playback" program the would work. This question is not about source code, so it is off-topic for SO. Consult your foo.exe user documentation. Commented Sep 21, 2021 at 19:13
  • Please use the fortran tag for all Fortran questions. Fortran 90 is just one very old revision of the standard. Commented Sep 24, 2021 at 16:26

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For windows cmd, just you can use a for loop.

(for %i in (2 y) do @echo %i)|C:\my\file\path\foo.exe Enter 1,2,3 for cat,dog,fish woof Enter y,n for yay,nay yes

If you are putting this in a .bat or .cmd, remember to use two % signs. There are lots of ways of doing this. See How can I echo a newline in a batch file?

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thank you so much, exactly what I was looking for
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You have two simple read statements. Each reads one record = one line of text. You need to provide two records or let the program continue at the old record.

In I can do echo -e "2 \n y" | ./a.out to get two records into one echo command, but I am not sure about Windows cmd. In Powershell you should use Echo newline to powershell console. That means

echo "2 `n y"

If you can change your Fortran code, use non-advancing input:

read (*,'(i1)',advance="no") n

With this change I can do

> echo -e "2 y" | ./a.out Enter 1,2,3 for cat,dog,fish woof

Tested in bash, but should work elsewhere including cmd.

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