Section: Misc. Reference Manual Pages (3PCAP)
Updated: 25 July 2018
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This man page documents libpcap version 1.9.1.

Your system may have a different version installed, possibly with some local modifications. To achieve the best results, please make sure this version of this man page suits your needs. If necessary, try to look for a different version on this web site or in the man pages available in your installation.


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);


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) will, if no packets are currently available to be read, return 0 immediately rather than blocking waiting for packets to arrive. pcap_loop(3PCAP) and pcap_next(3PCAP) will not work in ``non-blocking'' mode.

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.  


pcap_getnonblock() returns the current ``non-blocking'' state of the capture descriptor; it always returns 0 on ``savefiles''. If there is an 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.  


pcap(3PCAP), pcap_next_ex(3PCAP), pcap_geterr(3PCAP)

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