lex: add examples and add {Free,Net,Open}BSD pages (#11895)

* lex: add examples and add other BSD

* lex: fix OpenBSD man link

* lex: remove unsupported option from OpenBSD

* lex: apply suggestions from code review

Co-authored-by: Juri Dispan <juri.dispan@posteo.net>
Co-authored-by: K.B.Dharun Krishna <kbdharunkrishna@gmail.com>

* flex, lex: moving flex options to common/flex.md

* lex: mention `lex` alias to `flex`

* Update pages/linux/lex.md

---------

Co-authored-by: Juri Dispan <juri.dispan@posteo.net>
Co-authored-by: K.B.Dharun Krishna <kbdharunkrishna@gmail.com>

pages/common/flex.md

@@ -1,17 +1,26 @@
 # flex
 
-> Lexical analyzer generator. Based on `lex`.
+> Lexical analyzer generator. A rewrite of `lex` with extensions to the POSIX specification.
 > Given the specification for a lexical analyzer, generates C code implementing it.
+> NOTE: long options don't work on OpenBSD.
 > More information: <https://manned.org/flex>.
 
-- Generate an analyzer from a flex file:
+- Generate an analyzer from a flex file, storing it to the file `lex.yy.c`:
 
-`flex {{analyzer.l}}`
+`lex {{analyzer.l}}`
+
+- Write analyzer to `stdout`:
+
+`lex -{{-stdout|t}} {{analyzer.l}}`
 
 - Specify the output file:
 
-`flex --outfile {{analyzer.c}} {{analyzer.l}}`
+`lex {{analyzer.l}} -o {{analyzer.c}}`
 
-- Compile a C file generated by flex:
+- Generate a [B]atch scanner instead of an interactive scanner:
+
+`lex -B {{analyzer.l}}`
+
+- Compile a C file generated by Lex:
 
 `cc {{path/to/lex.yy.c}} --output {{executable}}`

pages/common/lex.md

@@ -2,9 +2,10 @@
 
 > Lexical analyzer generator.
 > Given the specification for a lexical analyzer, generates C code implementing it.
+> NOTE: on most major OSes, this command is an alias for `flex`.
 > More information: <https://manned.org/lex.1>.
 
-- Generate an analyzer from a Lex file:
+- Generate an analyzer from a Lex file, storing it to the file `lex.yy.c`:
 
 `lex {{analyzer.l}}`
 

pages/linux/lex.md

@@ -4,14 +4,22 @@
 > 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:
+- Generate an analyzer from a Lex file, storing it to the file `lex.yy.c`:
 
 `lex {{analyzer.l}}`
 
+- Write analyzer to `stdout`:
+
+`lex -{{-stdout|t}} {{analyzer.l}}`
+
 - Specify the output file:
 
 `lex {{analyzer.l}} --outfile {{analyzer.c}}`
 
+- Generate a [B]atch scanner instead of an interactive scanner:
+
+`lex -B {{analyzer.l}}`
+
 - Compile a C file generated by Lex:
 
 `cc {{path/to/lex.yy.c}} --output {{executable}}`

pages/osx/lex.md

@@ -1,17 +0,0 @@
-# lex
-
-> Lexical analyzer generator.
-> Given the specification for a lexical analyzer, generates C code implementing it.
-> More information: <https://keith.github.io/xcode-man-pages/lex.1.html>.
-
-- Generate an analyzer from a Lex file:
-
-`lex {{analyzer.l}}`
-
-- Specify the output file:
-
-`lex {{analyzer.l}} --outfile {{analyzer.c}}`
-
-- Compile a C file generated by Lex:
-
-`cc {{path/to/lex.yy.c}} --output {{executable}}`