Details

• The first argument (nfds) represents the number of bits in the masks that will be processed. Typically, this is 1 + the value of the highest fd

• The three fd_set arguments are bit masks … their manipulation is discussed on the next slide

• The last argument specifies the amount of time the select call should wait before completing its action and returning:

  • if NULL, select will wait (block) indefinitely until one of the file descriptors is ready for i/o
  • if tv_sec and tv_usec are zero, select will return immediately
  • if timeval members are non-zero, the system will wait the specified time or until a file descriptor is ready for i/o

• select() returns the number or file descriptors ready for i/o

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