How to write Antlr4 grammar rule to match file path? - regex

Question

What is the best method to write antlr4 grammar to match file paths like
"C:\Users\Alex\IdeaProjects\Compiler_Project\antlrTest\src\SQL.g4"
Or relative path like
"Compiler_Project//samples//test.txt"

Answer 1

My guess is you are trying to parse some sort of scripting language, like bash or zsh.
I agree that Antlr might not be the best choice to merely parse a file path, but that wasn't your question was it?
Here is a grammar excerpt from a larger grammar that parses windows batch files.
It's worth noting again that Antlr might not be the best choice for parsing Windows batch commands either in that each command can have peculiar syntax that doesn't readily apply to all the commands in a batch file.
That doesn't mean you can't do it though! Here, I use the 'island grammar' feature which requires separate lexer.g4 and grammar.g4 files but allows you to treat each command as its own little grammer.
Token reuse is a little awkward but not horrible.
BatchLexer.g4
lexer grammar BatchLexer;
options {
caseInsensitive=true;
}
CD : ('CD' | 'CHDIR') -> pushMode(CD_CMD) ;
DOT : '.' ;
DOTDOT : '..' ;
BLANK_LINE : NL ;
NL : '\n';
OPTION : '/' [a-z]+? ;
DRIVE : [a-z] ':' ; //posix?
WS : [ \t\r]+ ->skip ;
// This introduces the type name, but doesn't match anything at this scope
PATH : ~[.] ;
fragment ESCAPED_QUOTE : '\\"' ;
fragment PATH_WORD : ~[ <>:/|\r\n]+ ;
fragment RAW_PATH : DRIVE? (DOT | DOTDOT | ESCAPED_QUOTE | PATH_WORD) ;
fragment QUOTED_PATH : '"' DRIVE? (DOT | DOTDOT | ESCAPED_QUOTE | PATH_WORD) '"' ;
mode CD_CMD ;
CD_OPTION : OPTION -> type(OPTION) ;
CD_PATH : (RAW_PATH | QUOTED_PATH) -> type(PATH) ;
CD_NL : NL -> type(NL), popMode ;
CD_WS : WS ->skip ;
Batch.g4
grammar Batch;
options {
tokenVocab=BatchLexer;
caseInsensitive=true;
}
file : (command)* EOF ;
command : (
cd_cmd
)? (NL | BLANK_LINE) ;
cd_cmd : CD OPTION? PATH*? ;