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fd_set set;
FD_ZERO(&set);
FD_SET(fd, &set);
FD_CLR(fd, &set);
FD_ISSET(fd, &set);
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int select(int nfds, fd_set *readset, fd_set *writeset,
fd_set *exceptset, struct timeval *timeout);
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nfds
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readset
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writeset
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exceptset
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timeout
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int getitimer(int which, struct itimerval *value);
int setitimer(int which, const struct itimerval *value, struct itimerval *ovalue);
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