Linux From Scratch - Version 8.1-systemd

Chapter 6. Installing Basic System Software

6.32. Flex-2.6.4

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

Approximate build time: 0.4 SBU
Required disk space: 32 MB

6.32.1. Installation of Flex

First, fix a problem introduced with glibc-2.26: 

sed -i "/math.h/a #include <malloc.h>" src/flexdef.h

The build procedure assumes the help2man program is available to create a man page from the executable --help option. This is not present, so we use an environment variable to skip this process. Now, prepare Flex for compilation: 

HELP2MAN=/tools/bin/true \
./configure --prefix=/usr --docdir=/usr/share/doc/flex-2.6.4

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 symbolic link named lex that runs flex in lex emulation mode: 

ln -sv flex /usr/bin/lex

6.32.2. Contents of Flex

Installed programs: flex, flex++ (link to flex), and lex (link to flex)
Installed libraries: libfl.so and libfl_pic.so
Installed directory: /usr/share/doc/flex-2.6.4

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

The flex library