Linux From Scratch - Version 7.5-systemd-rc1

Chapter 6. Installing Basic System Software

6.32. Flex-2.5.38

The Flex package contains a utility for generating programs that recognize patterns in text.

Approximate build time: 0.4 SBU
Required disk space: 39 MB

6.32.1. Installation of Flex

First, skip running three regression tests that require bison. 

sed -i -e '/test-bison/d' tests/Makefile.in

Prepare Flex for compilation: 

./configure --prefix=/usr    \
            --docdir=/usr/share/doc/flex-2.5.38

Compile the package: 

make

To test the results (about 0.5 SBU), issue: 

make check

Install the package: 

make install

A few programs do not know about flex yet and try to run its predecessor, lex. To support those programs, create a wrapper 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 -v 755 /usr/bin/lex

6.32.2. Contents of Flex

Installed programs: flex, flex++ (link to flex), and lex
Installed libraries: libfl.{so,a} and libfl_pic.{so.a}
Installed directories: /usr/share/doc/flex-2.5.38

Short Descriptions

flex

A tool for generating programs that recognize patterns in text; it allows for the versatility to specify the rules for pattern-finding, eradicating the need to develop a specialized program

flex++

An extension of flex, is used for generating C++ code and classes. It is a symbolic link to flex

lex

A script that runs flex in lex emulation mode

libfl.so

The flex library