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  20 .TH PCAP_DUMP_OPEN 3PCAP "23 August 2018"
  21 .SH NAME
  22 pcap_dump_open, pcap_dump_open_append, pcap_dump_fopen \- open a file to
  23 which to write packets
  24 .SH SYNOPSIS
  25 .nf
  26 .ft B
  27 #include <pcap/pcap.h>
  28 .ft
  29 .nf
  30 .LP
  31 .ft B
  32 pcap_dumper_t *pcap_dump_open(pcap_t *p, const char *fname);
  33 pcap_dumper_t *pcap_dump_open_append(pcap_t *p, const char *fname);
  34 pcap_dumper_t *pcap_dump_fopen(pcap_t *p, FILE *fp);
  35 .ft
  36 .fi
  37 .SH DESCRIPTION
  38 .BR pcap_dump_open ()
  39 is called to open a ``savefile'' for writing.
  40 .I fname
  41 specifies the name of the file to open. The file will have
  42 the same format as those used by
  43 .BR tcpdump (1)
  44 and
  45 .BR tcpslice (1).
  46 The name "-" is a synonym
  47 for
  48 .BR stdout .
  49 .PP
  50 .BR pcap_dump_fopen ()
  51 is called to write data to an existing open stream
  52 .IR fp ;
  53 this stream will be closed by a subsequent call to
  54 .BR pcap_dump_close (3PCAP).
  55 Note that on Windows, that stream should be opened in binary mode.
  56 .PP
  57 .I p
  58 is a capture or ``savefile'' handle returned by an earlier call to
  59 .BR pcap_create (3PCAP)
  60 and activated by an earlier call to
  61 .BR \%pcap_activate (3PCAP),
  62 or returned by an earlier call to
  63 .BR \%pcap_open_offline (3PCAP),
  64 .BR pcap_open_live (3PCAP),
  65 or
  66 .BR pcap_open_dead (3PCAP).
  67 The time stamp precision, link-layer type, and snapshot length from
  68 .I p
  69 are used as the link-layer type and snapshot length of the output file.
  70 .PP
  71 .BR pcap_dump_open_append ()
  72 is like
  73 .BR pcap_dump_open ()
  74 but does not create the file if it does not exist and, if it does
  75 already exist, and is a pcap file with the same byte order as the host
  76 opening the file, and has the same time stamp precision, link-layer
  77 header type, and snapshot length as
  78 .IR p ,
  79 it will write new packets at the end of the file.
  80 .SH RETURN VALUES
  81 A pointer to a
  82 .B pcap_dumper_t
  83 structure to use in subsequent
  84 .BR pcap_dump (3PCAP)
  85 and
  86 .BR pcap_dump_close (3PCAP)
  87 calls is returned on success.
  88 .B NULL
  89 is returned on failure.
  90 If
  91 .B NULL
  92 is returned,
  93 .BR pcap_geterr (3PCAP)
  94 can be used to get the error text.
  95 .SH BACKWARD COMPATIBILITY
  96 .PP
  97 The
  98 .BR pcap_dump_open_append ()
  99 function became available in libpcap release 1.7.2.  In previous
 100 releases, there is no support for appending packets to an existing
 101 savefile.
 102 .SH SEE ALSO
 103 .BR pcap (3PCAP),
 104 .BR \%pcap-savefile (@MAN_FILE_FORMATS@)