How to save the output of an interactive command-line program in a Unix-like shell?

I am coding in C and running the programs in a Linux terminal. I want to save the output of the program in a .txt file. I usually do this by executing ./a.out>filen开发者_如何学运维ame.txt

But I have written an interactive program in which I have to enter a number to initiate the program. In that case how do I do it?

Thanks a lot and your valuable suggestions are most welcomed.

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Move the requirement to enter a number from the terminal to a command line parameter.

./a.out 42 > filename.txt

Or, easier, accept the input from a redirected input

echo 42 | ./a.out > filename.txt
./a.out < input.txt > filename.txt

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Try this

./a.out | tee filename.txt

Tee man page

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You can use script to capture all output to a file.

$ man script

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Assuming you have enter the number you wish to pass the to the program in an file called 'input.txt'. If you want to re-direct the output to 'output.txt', then type at the command-line:

./a.out  <  input.txt  >  output.txt