Updated: 2022/Sep/29

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PCAP_COMPILE(3)            Library Functions Manual            PCAP_COMPILE(3)



NAME
       pcap_compile - compile a filter expression

SYNOPSIS
       #include <pcap/pcap.h>

       int pcap_compile(pcap_t *p, struct bpf_program *fp,
               const char *str, int optimize, bpf_u_int32 netmask);

DESCRIPTION
       pcap_compile() is used to compile the string str into a filter program.
       See pcap-filter(7) for the syntax of that string.  fp is a pointer to a
       bpf_program struct and is filled in by pcap_compile().  optimize
       controls whether optimization on the resulting code is performed.
       netmask specifies the IPv4 netmask of the network on which packets are
       being captured; it is used only when checking for IPv4 broadcast
       addresses in the filter program.  If the netmask of the network on
       which packets are being captured isn't known to the program, or if
       packets are being captured on the Linux "any" pseudo-interface that can
       capture on more than one network, a value of PCAP_NETMASK_UNKNOWN can
       be supplied; tests for IPv4 broadcast addresses will fail to compile,
       but all other tests in the filter program will be OK.

       NOTE: in libpcap 1.8.0 and later, pcap_compile() can be used in
       multiple threads within a single process.  However, in earlier versions
       of libpcap, it is not safe to use pcap_compile() in multiple threads in
       a single process without some form of mutual exclusion allowing only
       one thread to call it at any given time.

RETURN VALUE
       pcap_compile() returns 0 on success and PCAP_ERROR on failure. If
       PCAP_ERROR is returned, pcap_geterr(3) or pcap_perror(3) may be called
       with p as an argument to fetch or display the error text.

BACKWARD COMPATIBILITY
       The PCAP_NETMASK_UNKNOWN constant became available in libpcap release
       1.1.0.

SEE ALSO
       pcap(3), pcap_setfilter(3), pcap_freecode(3)



                                22 August 2018                 PCAP_COMPILE(3)