c - fprintf both to file and to stdout -

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• how print both stdout , file in c 4 answers

my c program expected produce lot of output.

some of these output lines special , write copy special file. end doing

file * outf = fopen("special_file", "a"); fprintf(stdout, "normal line 1\n"); fprintf(stdout, "special line!\n"); fprintf(outf,   "special line!\n");/*inelegant & dangerous code duplication*/ fprintf(stdout, "normal line 2\n"); 

is there easy way avoid such inelegant & dangerous code duplication? have quite lot of , may write things printf("next %d\n", num++); cannot duplicated naively, e.g. using macros.

at moment see no solution short of spawning child process run tee equivalent. other idea? e.g. can 1 define kind of file* in way redirect both stdout & outf?

i think dup(2) system call need, see "man 2 dup".

edit: votes, think got wrong.

what dup make 2 file descriptors reference 1 file. want single file descriptor-like object references 2 files. that's quite different thing.