Why does my compiler not accept fork(), despite my inclusion of ?

Question

Here\'s my code (created just to test fork()):

#include   
#include 
#include 
#include 
#inclu         


        

Answer 1

As you've already noted, fork() should be defined in unistd.h - at least according to the man pages that come with Ubuntu 11.10. The minimal:

#include 

int main( int argc, char* argv[])
{
    pid_t procID;

    procID = fork();
    return procID;
}

...builds with no warnings on 11.10.

Speaking of which, what UNIX/Linux distribution are you using? For instance, I've found several non-remarkable functions that should be defined in Ubuntu 11.10's headers aren't. Such as:

// string.h
char* strtok_r( char* str, const char* delim, char** saveptr);
char* strdup( const char* const qString);

// stdio.h
int fileno( FILE* stream);

// time.h
int nanosleep( const struct timespec* req, struct timespec* rem);

// unistd.h
int getopt( int argc, char* const argv[], const char* optstring);
extern int opterr;
int usleep( unsigned int usec);

As long as they're defined in your C library it won't be a huge problem. Just define your own prototypes in a compatibility header and report the standard header problems to whoever maintains your OS distribution.