Rerouting stdin and stdout from C

I want to reopen the stdin and stdout (and perhaps stderr while I'm at it) filehandles, so that future calls to printf() or putchar() or puts() will go to a file, and future calls to getc() and such will come from a file. 1) I don't want to permanently lose standard input/output/error. I may want to reuse them later in the program. 2) I don't want to open new filehandles because these filehandles

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