pcap_open_live(3PCAP) man page

pcap_open_live(3PCAP) man page

Updated: 6 September 2026 • View in plain text • Return to Main Contents

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 capture packets on a device (typically a network interface, see pcap_findalldevs(3PCAP) for a more detailed explanation). device is a string that specifies the capture device to open; in this function, a null pointer means the same as the string “any”.

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 128MiB (128*1024*1024).

promisc specifies whether the device 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(3PCAP) 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 a null pointer on failure. If a null pointer 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(3PCAP), pcap_activate(3PCAP)

COLOPHON

This HTML man page was generated at 15:15:21 GMT, September 13, 2026 from a source man page in “The Tcpdump Group” git repositories using man2html and other tools.