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.TH PCAP_OPEN_LIVE 3PCAP "4 March 2024"
.SH NAME
pcap_open_live \- open a device for capturing
.SH SYNOPSIS
.nf
.ft B
#include <pcap/pcap.h>
.ft
.LP
.nf
.ft B
char errbuf[PCAP_ERRBUF_SIZE];
.ft
.LP
.ft B
pcap_t *pcap_open_live(const char *device, int snaplen,
    int promisc, int to_ms, char *errbuf);
.ft
.fi
.SH DESCRIPTION
.BR pcap_open_live ()
is used to obtain a packet capture handle to look
at packets on the network.
.I 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
.I device
argument of "any" or
.B 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
.BR pcap_findalldevs (3PCAP),
which may also include D-Bus, USB etc.
.PP
.I 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).
.PP
.I promisc
specifies whether the interface is to be put into promiscuous mode.
If
.I promisc
is non-zero, promiscuous mode will be set, otherwise it will not be set.
.PP
.I to_ms
specifies the packet buffer timeout, as a non-negative value, in
milliseconds.  (See
.BR pcap (3PCAP)
for an explanation of the packet buffer timeout.)
.PP
.I errbuf
is a buffer large enough to hold at least
.B PCAP_ERRBUF_SIZE
chars.
.SH RETURN VALUE
.BR pcap_open_live ()
returns a
.B pcap_t *
on success and
.B NULL
on failure.
If
.B NULL
is returned,
.I errbuf
is filled in with an appropriate error message.
.I errbuf
may also be set to warning text when
.BR pcap_open_live ()
succeeds; to detect this case the caller should store a zero-length string in
.I errbuf
before calling
.BR pcap_open_live ()
and display the warning to the user if
.I errbuf
is no longer a zero-length string.
.SH SEE ALSO
.BR pcap_create (3PCAP),
.BR pcap_activate (3PCAP)