Simulate the Linux command tee in C

Question

I have to do the simulation of the command tee in C for Linux. How does tee work internally? It looks like a T-shaped pipe, so should I use a pipe? Is

Answer 1

Here is some code I wrote about 20 years ago to implement TEE in Windows. I have been using this with various batch files since then. Note the flush command at the end of each line.

#include 
#include 

int main (int argc, char * argv[])
{
    if (argc < 2 )
    {
        printf ("Error:  No output file name given, example:  theCmd 2>&1 |ltee outputFileName \n");
        return 1;
    }
    FILE *Out = _fsopen(argv[argc-1], "a", _SH_DENYWR);
    if (NULL == Out)
    {
        char buf[300];
        sprintf_s(buf, 300, "Error openning %s", argv[argc-1]);
        perror(buf);
        return 1;
    }
    int ch;
    while ( EOF != (ch=getchar()))
    {
        putchar(ch);
        putc(ch, Out);
        if ( '\n' == ch )
            fflush(Out);
    }
    _flushall();
    fclose(Out);
    return 0;
}