Prepare Flex for compilation: ./configure --prefix=/usr Compile the package: make This package has a test suite available which can perform a number of checks to ensure it built correctly. Should you choose to run it, the following command will do so: make bigcheck And install the package: make install There are some packages that expect to find the Lex library in /usr/lib. Create a symlink to account for this: ln -s libfl.a /usr/lib/libl.a A few programs don't know about flex yet and try to run its predecessor lex. To support those programs, create a shell script named lex that calls flex in Lex emulation mode: cat > /usr/bin/lex << "EOF" #!/bin/sh # Begin /usr/bin/lex exec /usr/bin/flex -l "$@" # End /usr/bin/lex EOF chmod 755 /usr/bin/lex