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pcap_setnonblock, pcap_getnonblock - set or get the state of non-blocking mode on a capture device

#include <pcap/pcap.h>

char errbuf[PCAP_ERRBUF_SIZE];

int pcap_setnonblock(pcap_t *p, int nonblock, char *errbuf);
int pcap_getnonblock(pcap_t *p, char *errbuf);

 DESCRIPTION
 pcap_setnonblock () puts a capture handle into ``non-blocking'' mode, or takes it out
of ``non-blocking'' mode, depending on whether the
 nonblock argument is non-zero or zero. It has no effect on ``savefiles''.
If there is an error,
 PCAP_ERROR is returned and
 errbuf is filled in with an appropriate error message; otherwise,
 0 is returned.

In
``non-blocking'' mode, an attempt to read from the capture descriptor
with
 pcap_dispatch (3PCAP) and
 pcap_next_ex (3PCAP) will, if no packets are currently available to be read, return
 0 immediately rather than blocking waiting for packets to arrive.

 pcap_loop (3PCAP) will loop forever, consuming CPU time when no packets are currently
available;
 pcap_dispatch () should be used instead.
 pcap_next (3PCAP) will return
 NULL if there are no packets currently available to read;
this is indistinguishable from an error, so
 pcap_next_ex () should be used instead.

When first activated with
 pcap_activate (3PCAP) or opened with
 pcap_open_live (3PCAP) , a capture handle is not in ``non-blocking mode''; a call to
 pcap_setnonblock () is required in order to put it into ``non-blocking'' mode.
 RETURN VALUE
 pcap_getnonblock () returns the current ``non-blocking'' state of the capture descriptor; it
always returns
 0 on ``savefiles''.
If called on a capture handle that has been created but not activated,
 PCAP_ERROR_NOT_ACTIVATED is returned.
If there is another error,
 PCAP_ERROR is returned and
 errbuf is filled in with an appropriate error message.

 errbuf is assumed to be able to hold at least
 PCAP_ERRBUF_SIZE chars.
 SEE ALSO
 pcap (3PCAP),  pcap_next_ex (3PCAP),  pcap_geterr (3PCAP)