6.43. Flex-2.5.37

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

6.43.1. Installation of Flex

First, fix some regression tests:

patch -Np1 -i ../flex-2.5.37-bison-2.6.1-1.patch

Prepare Flex for compilation:

./configure --prefix=/usr --mandir=/usr/share/man --infodir=/usr/share/info

Compile the package:


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

make -k check

There are two tests that fail due to incompatibilities with the most recent version of bison.

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 -sv libfl.a /usr/lib/libl.a

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"
# Begin /usr/bin/lex

exec /usr/bin/flex -l "$@"

# End /usr/bin/lex
chmod -v 755 /usr/bin/lex

If desired, install the flex.pdf documentation file:

mkdir -v /usr/share/doc/flex-2.5.37
cp    -v doc/flex.pdf /usr/share/doc/flex-2.5.37

6.43.2. Contents of Flex

Installed programs: flex and lex
Installed libraries: libfl.a and libfl_pic.a

Short Descriptions


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


A script that runs flex in lex emulation mode


The flex library