Update cheatsheets

tldr/linux/flex

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+---
+syntax: markdown
+tags: [tldr, linux]
+source: https://github.com/tldr-pages/tldr.git
+---
+# flex
+
+> Lexical analyzer generator.
+> Given the specification for a lexical analyzer, generates C code implementing it.
+> More information: <https://manned.org/lex.1>.
+
+- Generate an analyzer from a Lex file, storing it to the file `lex.yy.c`:
+
+`flex {{analyzer.l}}`
+
+- Write analyzer to `stdout`:
+
+`flex {{[-t|--stdout]}} {{analyzer.l}}`
+
+- Specify the output file:
+
+`flex {{analyzer.l}} {{[-o|--outfile]}} {{analyzer.c}}`
+
+- Generate a batch scanner instead of an interactive scanner:
+
+`flex {{[-B|--batch]}} {{analyzer.l}}`
+
+- Compile a C file generated by Lex:
+
+`cc {{path/to/lex.yy.c}} -o {{executable}}`