root@localhost flex-2.5.4]# ./configure
creating cache ./config.cache
checking whether ln -s works... yes
checking for bison... no
checking for byacc... no
checking for gcc... gcc
checking whether we are using GNU C... yes
checking whether gcc accepts -g... yes
checking for ranlib... ranlib
checking for a BSD compatible install... /usr/bin/install -c
checking whether make sets $MAKE... yes
checking for working const... yes
checking how to run the C preprocessor... gcc -E
checking whether cross-compiling... no
checking for ANSI C header files... yes
checking for size_t... yes
checking for ANSI C header files... (cached) yes
checking for string.h... yes
checking for malloc.h... yes
checking for sys/types.h... yes
updating cache ./config.cache
creating ./config.status
creating Makefile
creating config.h
[root@localhost flex-2.5.4]# make
cp ./initscan.c scan.c
touch .bootstrap
gcc -c -I. -I. -g -O ccl.c
gcc -c -I. -I. -g -O dfa.c
gcc -c -I. -I. -g -O ecs.c
gcc -c -I. -I. -g -O gen.c
gcc -c -I. -I. -g -O main.c
gcc -c -I. -I. -g -O misc.c
gcc -c -I. -I. -g -O nfa.c
yacc -d ./parse.y
make: yacc: Command not found
make: *** [parse.c] Error 127
[root@localhost flex-2.5.4]#