Lexical Analysis With Flex, for Flex 2.6.4

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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 2.6.4. It was last updated on 6 May 2017.

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

• Copyright:  
• Reporting Bugs:  
• Introduction:  
• Simple Examples:  
• Format:  
• Patterns:  
• Matching:  
• Actions:  
• Generated Scanner:  
• Start Conditions:  
• Multiple Input Buffers:  
• EOF:  
• Misc Macros:  
• User Values:  
• Yacc:  
• Scanner Options:  
• Performance:  
• Cxx:  
• Reentrant:  
• Lex and Posix:  
• Memory Management:  
• Serialized Tables:  
• Diagnostics:  
• Limitations:  
• Bibliography:  
• FAQ:  
• Appendices:  
• Indices:   


 — The Detailed Node Listing —

Format of the Input File
• Definitions Section:  
• Rules Section:  
• User Code Section:  
• Comments in the Input:   

Scanner Options
• Options for Specifying Filenames:  
• Options Affecting Scanner Behavior:  
• Code-Level And API Options:  
• Options for Scanner Speed and Size:  
• Debugging Options:  
• Miscellaneous Options:   

Reentrant C Scanners
• Reentrant Uses:  
• Reentrant Overview:  
• Reentrant Example:  
• Reentrant Detail:  
• Reentrant Functions:   

The Reentrant API in Detail
• Specify Reentrant:  
• Extra Reentrant Argument:  
• Global Replacement:  
• Init and Destroy Functions:  
• Accessor Methods:  
• Extra Data:  
• About yyscan_t:   

Memory Management
• The Default Memory Management:  
• Overriding The Default Memory Management:  
• A Note About yytext And Memory:   

Serialized Tables
• Creating Serialized Tables:  
• Loading and Unloading Serialized Tables:  
• 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 cant I use fast or full tables with interactive mode?:  
• How much faster is -F or -f than -C?:  
• If I have a simple grammar cant 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 period 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()?:  
• How do I use my own I/O classes in a C++ scanner?:  
• How do I skip as many chars as possible?:  
• deleteme00:  
• Are certain equivalent patterns faster than others?:  
• Is backing up a big deal?:  
• Can I fake multi-byte character support?:  
• deleteme01:  
• 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?:  
• ERASEME53:  
• I need to scan if-then-else blocks and while loops:  
• ERASEME55:  
• ERASEME56:  
• ERASEME57:  
• 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
• Makefiles and Flex:  
• Bison Bridge:  
• M4 Dependency:  
• 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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