flex

This manual describes flex, a tool for generating programs that perform pattern-matching on text. The manual includes both tutorial and reference sections.

This edition of The flex Manual documents flex version 2.5.37. It was last updated on 22 July 2012.

This manual was written by Vern Paxson, Will Estes and John Millaway.

— The Detailed Node Listing — Format of the Input File
1. Copyright
2. Reporting Bugs
3. Introduction
4. Some Simple Examples
5. Format of the Input File
6. Patterns
7. How the Input Is Matched
8. Actions
9. The Generated Scanner
10. Start Conditions
11. Multiple Input Buffers
12. End-of-File Rules
13. Miscellaneous Macros
14. Values Available To the User
15. Interfacing with Yacc
16. Scanner Options
17. Performance Considerations
18. Generating C++ Scanners
19. Reentrant C Scanners
20. Incompatibilities with Lex and Posix
21. Memory Management
22. Serialized Tables
23. Diagnostics
24. Limitations
25. Additional Reading
FAQ
A. Appendices
Indices
5.1 Format of the Definitions Section
5.2 Format of the Rules Section
5.3 Format of the User Code Section
5.4 Comments in the Input
Scanner Options
16.1 Options for Specifying Filenames
16.2 Options Affecting Scanner Behavior
16.3 Code-Level And API Options
16.4 Options for Scanner Speed and Size
16.5 Debugging Options
16.6 Miscellaneous Options
Reentrant C Scanners
19.1 Uses for Reentrant Scanners
19.2 An Overview of the Reentrant API
19.3 Reentrant Example
19.4 The Reentrant API in Detail
19.5 Functions and Macros Available in Reentrant C Scanners
The Reentrant API in Detail
19.4.1 Declaring a Scanner As Reentrant
19.4.2 The Extra Argument
19.4.3 Global Variables Replaced By Macros
19.4.4 Init and Destroy Functions
19.4.5 Accessing Variables with Reentrant Scanners
19.4.6 Extra Data
19.4.7 About yyscan_t
Memory Management
21.1 The Default Memory Management
21.2 Overriding The Default Memory Management
21.3 A Note About yytext And Memory
Serialized Tables
22.1 Creating Serialized Tables
22.2 Loading and Unloading Serialized Tables
22.3 Tables File Format
FAQ
When was flex born?
How do I expand backslash-escape sequences in C-style quoted strings?
Why do flex scanners call fileno if it is not ANSI compatible?
Does flex support recursive pattern definitions?
How do I skip huge chunks of input (tens of megabytes) while using flex?
Flex is not matching my patterns in the same order that I defined them.
My actions are executing out of order or sometimes not at all.
How can I have multiple input sources feed into the same scanner at the same time?
Can I build nested parsers that work with the same input file?
How can I match text only at the end of a file?
How can I make REJECT cascade across start condition boundaries?
Why can’t I use fast or full tables with interactive mode?
How much faster is -F or -f than -C?
If I have a simple grammar can’t I just parse it with flex?
Why doesn’t yyrestart() set the start state back to INITIAL?
How can I match C-style comments?
The ’.’ isn’t working the way I expected.
Can I get the flex manual in another format?
Does there exist a "faster" NDFA->DFA algorithm?
How does flex compile the DFA so quickly?
How can I use more than 8192 rules?
How do I abandon a file in the middle of a scan and switch to a new file?
How do I execute code only during initialization (only before the first scan)?
How do I execute code at termination?
Where else can I find help?
Can I include comments in the "rules" section of the file?
I get an error about undefined yywrap().
How can I change the matching pattern at run time?
How can I expand macros in the input?
How can I build a two-pass scanner?
How do I match any string not matched in the preceding rules?
I am trying to port code from AT&T lex that uses yysptr and yysbuf.
Is there a way to make flex treat NULL like a regular character?
Whenever flex can not match the input it says "flex scanner jammed".
Why doesn’t flex have non-greedy operators like perl does?
Memory leak - 16386 bytes allocated by malloc.
How do I track the byte offset for lseek()?
25.1 How do I use my own I/O classes in a C++ scanner?
How do I skip as many chars as possible?
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Are certain equivalent patterns faster than others?
Is backing up a big deal?
Can I fake multi-byte character support?
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Can you discuss some flex internals?
unput() messes up yy_at_bol
The \| operator is not doing what I want
Why can’t flex understand this variable trailing context pattern?
The ^ operator isn’t working
Trailing context is getting confused with trailing optional patterns
Is flex GNU or not?
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I need to scan if-then-else blocks and while loops
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Is there a repository for flex scanners?
How can I conditionally compile or preprocess my flex input file?
Where can I find grammars for lex and yacc?
I get an end-of-buffer message for each character scanned.
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What is the difference between YYLEX_PARAM and YY_DECL?
Why do I get "conflicting types for yylex" error?
How do I access the values set in a Flex action from within a Bison action?
Appendices
A.1 Makefiles and Flex
A.2 C Scanners with Bison Parsers
A.3 M4 Dependency
A.4 Common Patterns
Indices
Concept Index
Index of Functions and Macros
Index of Variables
Index of Data Types
Index of Hooks
Index of Scanner Options

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