Updated: 2025/Nov/16

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PCAP_OPEN_LIVE(3)          Library Functions Manual          PCAP_OPEN_LIVE(3)

NAME
       pcap_open_live - open a device for capturing

SYNOPSIS
       #include <pcap/pcap.h>

       char errbuf[PCAP_ERRBUF_SIZE];

       pcap_t *pcap_open_live(const char *device, int snaplen,
           int promisc, int to_ms, char *errbuf);

DESCRIPTION
       pcap_open_live() is used to obtain a packet capture handle to look at
       packets on the network.  device is a string that specifies the network
       device to open; on all supported Linux systems, as well as on recent
       versions of macOS and Solaris, a device argument of "any" or NULL can
       be used to capture packets from all network interfaces.  The latter
       should not be confused with all available capture devices as seen by
       pcap_findalldevs(3), which may also include D-Bus, USB etc.

       snaplen specifies the snapshot length to be set on the handle.  If the
       packet data should not be truncated at the end, a value of 262144
       should be sufficient for most devices, but D-Bus devices require a
       value of 128MB (128*1024*1024).

       promisc specifies whether the interface is to be put into promiscuous
       mode.  If promisc is non-zero, promiscuous mode will be set, otherwise
       it will not be set.

       to_ms specifies the packet buffer timeout, as a non-negative value, in
       milliseconds.  (See pcap(3) for an explanation of the packet buffer
       timeout.)

       errbuf is a buffer large enough to hold at least PCAP_ERRBUF_SIZE
       chars.

RETURN VALUE
       pcap_open_live() returns a pcap_t * on success and NULL on failure.  If
       NULL is returned, errbuf is filled in with an appropriate error
       message.  errbuf may also be set to warning text when pcap_open_live()
       succeeds; to detect this case the caller should store a zero-length
       string in errbuf before calling pcap_open_live() and display the
       warning to the user if errbuf is no longer a zero-length string.

SEE ALSO
       pcap_create(3), pcap_activate(3)

                                 4 March 2024                PCAP_OPEN_LIVE(3)