# pcap_fopen_offline

## 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(1) 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_ ; this stream will be closed by a
           subsequent call to **pcap_close**(3PCAP) unless it is **stdin**.
           **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.
    
           _errbuf_ is a buffer large enough to hold at least **PCAP_ERRBUF_SIZE**
           chars.
    


## 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.
    


## 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.
    


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