41          microseconds in an argument of type struct timeval, whereas for the
  42          pselect() function the timeout period is given in seconds and
  43          nanoseconds in an argument of type struct timespec
  44 
  45      o   The select() function has no sigmask argument.  It behaves as
  46          pselect() does when sigmask is a null pointer.
  47 
  48      o   Upon successful completion, the select() function might modify the
  49          object pointed to by the Itimeout argument.
  50 
  51      The select() and pselect() functions support regular files, terminal and
  52      pseudo-terminal devices, STREAMS-based files, FIFOs, pipes, and sockets.
  53      The behavior of select() and pselect() on file descriptors that refer to
  54      other types of file is unspecified.
  55 
  56      The nfds argument specifies the range of file descriptors to be tested.
  57      The first nfds descriptors are checked in each set; that is, the
  58      descriptors from zero through ``nfds - 1'' in the descriptor sets are
  59      examined.
  60 
  61      If the readfs argument is not a null pointer, it points to an object of
  62      type fd_set that on input specifies the file descriptors to be checked
  63      for being ready to read, and on output indicates which file descriptors
  64      are ready to read.
  65 
  66      If the writefs argument is not a null pointer, it points to an object of
  67      type fd_set that on input specifies the file descriptors to be checked
  68      for being ready to write, and on output indicates which file descriptors
  69      are ready to write.
  70 
  71      If the errorfds argument is not a null pointer, it points to an object of
  72      type fd_set that on input specifies the file descriptors to be checked
  73      for error conditions pending, and on output indicates which file
  74      descriptors have error conditions pending.
  75 
  76      Upon successful completion, the objects pointed to by the readfs,
  77      writefs, and errorfds arguments are modified to indicate which file
  78      descriptors are ready for reading, ready for writing, or have an error
  79      condition pending, respectively, and return the total number of ready
  80      descriptors in all the output sets.  For each file descriptor less than
  81      nfds, the corresponding bit will be set on successful completion if it
  82      was set on input and the associated condition is true for that file
  83      descriptor.
  84 
  85      If none of the selected descriptors are ready for the requested
  86      operation, the select() or pselect() function blocks until at least one
  87      of the requested operations becomes ready, until the timeout occurs, or
  88      until interrupted by a signal.  The timeout parameter controls how long
  89      the select() or pselect() function takes before timing out.  If the
  90      timeout parameter is not a null pointer, it specifies a maximum interval
  91      to wait for the selection to complete.  If the specified time interval
  92      expires without any requested operation becoming ready, the function
  93      returns.  If the timeout parameter is a null pointer, then the call to
  94      select() or pselect() blocks indefinitely until at least one descriptor
  95      meets the specified criteria.  To effect a poll, the timeout parameter
  96      should not be a null pointer, and should point to a zero-valued timespec
  97      structure.

 151      A file descriptor for a socket that is listening for connections will
 152      indicate that it is ready for reading, when connections are available.  A
 153      file descriptor for a socket that is connecting asynchronously will
 154      indicate that it is ready for writing, when a connection has been
 155      established.
 156 
 157      Selecting true for reading on a socket descriptor upon which a
 158      listen(3XNET) call has been performed indicates that a subsequent
 159      accept(3XNET) call on that descriptor will not block.
 160 
 161      If the timeout argument is not a null pointer, it points to an object of
 162      type struct timeval that specifies a maximum interval to wait for the
 163      selection to complete.  If the timeout argument points to an object of
 164      type struct timeval whose members are 0, select() does not block.  If the
 165      timeout argument is a null pointer, select() blocks until an event causes
 166      one of the masks to be returned with a valid (non-zero) value.  If the
 167      time limit expires before any event occurs that would cause one of the
 168      masks to be set to a non-zero value, select() completes successfully and
 169      returns 0.
 170 
 171      If the readfs, writefds, and errorfds arguments are all null pointers and
 172      the timeout argument is not a null pointer, select() or pselect() blocks
 173      for the time specified, or until interrupted by a signal.  If the
 174      readfds, writefds, and errorfds arguments are all null pointers and the
 175      timeout argument is a null pointer, select() blocks until interrupted by
 176      a signal.
 177 
 178      File descriptors associated with regular files always select true for
 179      ready to read, ready to write, and error conditions.
 180 
 181      On failure, the objects pointed to by the readfds, writefds, and errorfds
 182      arguments are not modified.  If the timeout interval expires without the
 183      specified condition being true for any of the specified file descriptors,
 184      the objects pointed to by the readfds, writefds, and errorfds arguments
 185      have all bits set to 0.
 186 
 187      File descriptor masks of type fd_set can be initialized and tested with
 188      the macros FD_CLR(), FD_ISSET(), FD_SET(), and FD_ZERO().
 189 
 190      FD_CLR(fd, &fdset)
 191              Clears the bit for the file descriptor fd in the file descriptor
 192              set fdset.
 193 

  41          microseconds in an argument of type struct timeval, whereas for the
  42          pselect() function the timeout period is given in seconds and
  43          nanoseconds in an argument of type struct timespec
  44 
  45      o   The select() function has no sigmask argument.  It behaves as
  46          pselect() does when sigmask is a null pointer.
  47 
  48      o   Upon successful completion, the select() function might modify the
  49          object pointed to by the Itimeout argument.
  50 
  51      The select() and pselect() functions support regular files, terminal and
  52      pseudo-terminal devices, STREAMS-based files, FIFOs, pipes, and sockets.
  53      The behavior of select() and pselect() on file descriptors that refer to
  54      other types of file is unspecified.
  55 
  56      The nfds argument specifies the range of file descriptors to be tested.
  57      The first nfds descriptors are checked in each set; that is, the
  58      descriptors from zero through ``nfds - 1'' in the descriptor sets are
  59      examined.
  60 
  61      If the readfds argument is not a null pointer, it points to an object of
  62      type fd_set that on input specifies the file descriptors to be checked
  63      for being ready to read, and on output indicates which file descriptors
  64      are ready to read.
  65 
  66      If the writefds argument is not a null pointer, it points to an object of
  67      type fd_set that on input specifies the file descriptors to be checked
  68      for being ready to write, and on output indicates which file descriptors
  69      are ready to write.
  70 
  71      If the errorfds argument is not a null pointer, it points to an object of
  72      type fd_set that on input specifies the file descriptors to be checked
  73      for error conditions pending, and on output indicates which file
  74      descriptors have error conditions pending.
  75 
  76      Upon successful completion, the objects pointed to by the readfds,
  77      writefds, and errorfds arguments are modified to indicate which file
  78      descriptors are ready for reading, ready for writing, or have an error
  79      condition pending, respectively, and return the total number of ready
  80      descriptors in all the output sets.  For each file descriptor less than
  81      nfds, the corresponding bit will be set on successful completion if it
  82      was set on input and the associated condition is true for that file
  83      descriptor.
  84 
  85      If none of the selected descriptors are ready for the requested
  86      operation, the select() or pselect() function blocks until at least one
  87      of the requested operations becomes ready, until the timeout occurs, or
  88      until interrupted by a signal.  The timeout parameter controls how long
  89      the select() or pselect() function takes before timing out.  If the
  90      timeout parameter is not a null pointer, it specifies a maximum interval
  91      to wait for the selection to complete.  If the specified time interval
  92      expires without any requested operation becoming ready, the function
  93      returns.  If the timeout parameter is a null pointer, then the call to
  94      select() or pselect() blocks indefinitely until at least one descriptor
  95      meets the specified criteria.  To effect a poll, the timeout parameter
  96      should not be a null pointer, and should point to a zero-valued timespec
  97      structure.

 151      A file descriptor for a socket that is listening for connections will
 152      indicate that it is ready for reading, when connections are available.  A
 153      file descriptor for a socket that is connecting asynchronously will
 154      indicate that it is ready for writing, when a connection has been
 155      established.
 156 
 157      Selecting true for reading on a socket descriptor upon which a
 158      listen(3XNET) call has been performed indicates that a subsequent
 159      accept(3XNET) call on that descriptor will not block.
 160 
 161      If the timeout argument is not a null pointer, it points to an object of
 162      type struct timeval that specifies a maximum interval to wait for the
 163      selection to complete.  If the timeout argument points to an object of
 164      type struct timeval whose members are 0, select() does not block.  If the
 165      timeout argument is a null pointer, select() blocks until an event causes
 166      one of the masks to be returned with a valid (non-zero) value.  If the
 167      time limit expires before any event occurs that would cause one of the
 168      masks to be set to a non-zero value, select() completes successfully and
 169      returns 0.
 170 
 171      If the readfds, writefds, and errorfds arguments are all null pointers
 172      and the timeout argument is not a null pointer, select() or pselect()
 173      blocks for the time specified, or until interrupted by a signal.  If the
 174      readfds, writefds, and errorfds arguments are all null pointers and the
 175      timeout argument is a null pointer, select() blocks until interrupted by
 176      a signal.
 177 
 178      File descriptors associated with regular files always select true for
 179      ready to read, ready to write, and error conditions.
 180 
 181      On failure, the objects pointed to by the readfds, writefds, and errorfds
 182      arguments are not modified.  If the timeout interval expires without the
 183      specified condition being true for any of the specified file descriptors,
 184      the objects pointed to by the readfds, writefds, and errorfds arguments
 185      have all bits set to 0.
 186 
 187      File descriptor masks of type fd_set can be initialized and tested with
 188      the macros FD_CLR(), FD_ISSET(), FD_SET(), and FD_ZERO().
 189 
 190      FD_CLR(fd, &fdset)
 191              Clears the bit for the file descriptor fd in the file descriptor
 192              set fdset.
 193