You'll need "lex" and "yacc" or the gnu versions "flex" and "bison". If you receive errors while building snort or libpcap that refer to "lex" or "yacc", you can build the gnu versions as follows:

###########################
# BISON

download "bison-1.30.tar.gz" from "ftp.gnu.org"
you'll find it in the "/pub/gnu/bison" directory

# tar xvzf bison-1.30.tar.gz
# cd bison-1.30
# ./configure
# make
# make install


##########################
# FLEX

download "flex-2.5.4a.tar.gz" "ftp.gnu.org"
you'll find it in the "/pub/gnu/non-gnu/flex" directory

# tar zxvf flex-2.5.4a.tar.gz
# cd flex-2.5.4
# ./configure
# make
# make install


this version of flex seems to have errors in the makefile, if you receive errors while compiling, try these workarounds from your present working directory, then performing a "make" and "make install" again:

# mkdir usr
# mkdir usr/bin
# ln -s /usr/bin/install usr/bin/install

# ln -s /bin/ln /bin/n
(once you've made this program correctly, you can remove this link with "rm /bin/n")


if you are following these steps because of probelms while installing libpcap, you'll have to do a "make clean" in the base installation directory for libpcap, and then proceed with "make" and "make install" as instructed
