libpcap函数有问题吗？

#include <stdio.h>
#include <pcap.h>

int main(int argc,char* argv[])
{
    char* dev=argv[1];
    char errbuf[PCAP_ERRBUF_SIZE];
    dev=pcap_lookupdev(errbuf);
    if(dev==NULL) {
        fprintf(stderr,\"Couldn\'t find default device: %s\\n\",errbuf);
        return 0;   
    }
    printf(\"Device: %s\\n\",dev); 

    return 0;
}

$ cc pcap1.c 
/tmp/ccZLrRlF.o: In function `main\':
pcap1.c:(.text+0x37): undefined reference to `pcap_lookupdev\'
collect2: ld returned 1 exit status

libpcap