lfs-book/chapter06/flex.xml

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  <!ENTITY % general-entities SYSTEM "../general.ent">
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<sect1 id="ch-system-flex" xreflabel="Flex">
<title>Flex-&flex-version;</title>
<?dbhtml filename="flex.html"?>

<indexterm zone="ch-system-flex"><primary sortas="a-Flex">Flex</primary></indexterm>

<para>The Flex package contains a utility for generating programs that
recognize patterns in text.</para>

<screen>&buildtime; 0.1 SBU
&diskspace; 3.4 MB</screen>

<para>Flex installation depends on: Bash, Binutils, Bison, Coreutils, Diffutils,
GCC, Gettext, Glibc, Grep, M4, Make, Sed.</para>



<sect2>
<title>Installation of Flex</title>

<para>Prepare Flex for compilation:</para>

<screen><userinput>./configure --prefix=/usr</userinput></screen>

<para>Compile the package:</para>

<screen><userinput>make</userinput></screen>

<para>To test the results, issue:
<userinput>make bigcheck</userinput>.</para>

<para>Now install the package:</para>

<screen><userinput>make install</userinput></screen>

<para>There are some packages that expect to find the <emphasis>lex</emphasis>
library in <filename>/usr/lib</filename>. Create a symlink to account for
this:</para>

<screen><userinput>ln -s libfl.a /usr/lib/libl.a</userinput></screen>

<para>A few programs don't know about <command>flex</command> yet and try
to run its predecessor <command>lex</command>. To support those programs,
create a wrapper script named <filename>lex</filename> that calls
<command>flex</command> in <emphasis>lex</emphasis> emulation mode:</para>

<screen><userinput>cat &gt; /usr/bin/lex &lt;&lt; "EOF"</userinput>
#!/bin/sh
# Begin /usr/bin/lex

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

# End /usr/bin/lex
<userinput>EOF
chmod 755 /usr/bin/lex</userinput></screen>

</sect2>


<sect2 id="contents-flex"><title>Contents of Flex</title>

<para><emphasis>Installed programs</emphasis>: flex, flex++ (link to flex)
and lex</para>

<para><emphasis>Installed library</emphasis>: libfl.a</para>

</sect2>


<sect2><title>Short descriptions</title>

<indexterm zone="ch-system-flex flex"><primary sortas="b-flex">flex</primary></indexterm>
<para id="flex"><command>flex</command> is a tool for generating programs that
recognize patterns in text. Pattern recognition is useful in many applications.
From a set of rules on what to look for, flex makes a program that looks for
those patterns. The reason to use flex is that it is much easier to specify
the rules for a pattern-finding program than to write the program.</para>

<indexterm zone="ch-system-flex flex-"><primary sortas="b-flex++">flex++</primary></indexterm>
<para id="flex-"><command>flex++</command> invokes a version of flex that is used
exclusively for C++ scanners.</para>

<indexterm zone="ch-system-flex libfl.a"><primary sortas="c-libfl.a">libfl.a</primary></indexterm>
<para id="libfl.a"><command>libfl.a</command> is the flex library.</para>

</sect2>



</sect1>