Updated: 2021/Apr/14


PCAP_OPEN_OFFLINE(3)       Library Functions Manual       PCAP_OPEN_OFFLINE(3)



NAME
       pcap_open_offline, pcap_open_offline_with_tstamp_precision,
       pcap_fopen_offline, pcap_fopen_offline_with_tstamp_precision - open a
       saved capture file for reading

SYNOPSIS
       #include <pcap/pcap.h>

       char errbuf[PCAP_ERRBUF_SIZE];

       pcap_t *pcap_open_offline(const char *fname, char *errbuf);
       pcap_t *pcap_open_offline_with_tstamp_precision(const char *fname,
           u_int precision, char *errbuf);
       pcap_t *pcap_fopen_offline(FILE *fp, char *errbuf);
       pcap_t *pcap_fopen_offline_with_tstamp_precision(FILE *fp,
           u_int precision, char *errbuf);

DESCRIPTION
       pcap_open_offline() and pcap_open_offline_with_tstamp_precision() are
       called to open a ``savefile'' for reading.

       fname specifies the name of the file to open. The file can have the
       pcap file format as described in pcap-savefile(5), which is the file
       format used by, among other programs, tcpdump(8) and tcpslice(1), or
       can have the pcapng file format, although not all pcapng files can be
       read.  The name "-" is a synonym for stdin.

       pcap_open_offline_with_tstamp_precision() takes an additional precision
       argument specifying the time stamp precision desired; if
       PCAP_TSTAMP_PRECISION_MICRO is specified, packet time stamps will be
       supplied in seconds and microseconds, and if PCAP_TSTAMP_PRECISION_NANO
       is specified, packet time stamps will be supplied in seconds and
       nanoseconds.  If the time stamps in the file do not have the same
       precision as the requested precision, they will be scaled up or down as
       necessary before being supplied.

       Alternatively, you may call pcap_fopen_offline() or
       pcap_fopen_offline_with_tstamp_precision() to read dumped data from an
       existing open stream fp.  pcap_fopen_offline_with_tstamp_precision()
       takes an additional precision argument as described above.  Note that
       on Windows, that stream should be opened in binary mode.

RETURN VALUE
       pcap_open_offline(), pcap_open_offline_with_tstamp_precision(),
       pcap_fopen_offline(), and pcap_fopen_offline_with_tstamp_precision()
       return a pcap_t * on success and NULL on failure.  If NULL is returned,
       errbuf is filled in with an appropriate error message.  errbuf is
       assumed to be able to hold at least PCAP_ERRBUF_SIZE chars.

BACKWARD COMPATIBILITY
       pcap_open_offline_with_tstamp_precision and
       pcap_fopen_offline_with_tstamp_precision became available in libpcap
       release 1.5.1.  In previous releases, time stamps from a savefile are
       always given in seconds and microseconds.

SEE ALSO
       pcap(3), pcap-savefile(5)



                                8 January 2018            PCAP_OPEN_OFFLINE(3)