Redirect the stdout to buffer,not using >

Question

I wrote my implementation of printf – myPrintf,which prints to stdout. I want to verify that it works fine.In order to check the correctess of the printed output I want to compare it with char I expect to get. How can I write code to redirect the stdout to buffer,not using >.

I can use only printf!

Why are you opposed to teeing the output to a file with >? — Rob Marrowstone
– Rob Marrowstone, Commented Aug 16, 2011 at 14:45
If this is C++ why not use iostreams instead? Then "capturing" the output is simply a question of using a stringstream — Flexo - Save the data dump
– Flexo - Save the data dump ♦, Commented Aug 16, 2011 at 14:49
Without knowing what you are actually using to print it out, its hard to tell what to use to capture the output. — PlasmaHH
– PlasmaHH, Commented Aug 16, 2011 at 14:55

Community · Accepted Answer · 2017-05-23 12:33:15Z

You could redirect couts buffer by setting it's rdbuf() to a file you have opened.

Weird, C++ and only printf, but whatever.

It's also possible to redirect stdout in C.

Here is one way of doing it: https://rydow.wordpress.com/2007/10/26/c-code-to-redirect-stdout/

It involves dup and dup2.

There is also this option ( Rerouting stdin and stdout from C ) using freopen.

Or to a custom std::streambuf that copies into some place in memory (think std::ostringstream).

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