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How to divert file input to standard input?
Nov 2, 2010 at 9:05am
I've been working on c++ for some time and I know the basics. I know how to input from files with FILE and ifstream but my friend told me that there is a way to divert file input to standard input so I can read from a file with scanf. How do I do it?
Last edited on Nov 2, 2010 at 9:05am
Nov 2, 2010 at 11:40am
As above, you can open the file and use use fscanf where you previously used scanf.
Or you can use redirection as suggested. Redirection happens outside of your program, a program copies the file to stdout, and the shell redirects that stdout to the stdin in your program. The input appears as if you had typed it in.
Here's a Windows example. Select Start->Run and enter cmd.exe. This should give you a console.
Use notepad to create a file, data.txt, and enter some text:
You can see the content with type. type reads each line and writes it to stdout, which you see on the console.
To redirect that into your program, use a pipe. I'll assume your program is called myprog.exe and is in the currect directory.
Or you can use redirection as suggested. Redirection happens outside of your program, a program copies the file to stdout, and the shell redirects that stdout to the stdin in your program. The input appears as if you had typed it in.
Here's a Windows example. Select Start->Run and enter cmd.exe. This should give you a console.
Use notepad to create a file, data.txt, and enter some text:
notepad data.txtYou can see the content with type. type reads each line and writes it to stdout, which you see on the console.
type data.txtTo redirect that into your program, use a pipe. I'll assume your program is called myprog.exe and is in the currect directory.
type data.txt | myprog
Last edited on Nov 2, 2010 at 11:40am
Nov 2, 2010 at 9:19pm
That wasn't what I was looking for but never mind I found out that what I was looking for is
freopen()
freopen()
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