for DOS-based systems, "\n\r" is appropriate.

No.
\n is transformed to \r\n on output.
\r\n is transformed to \n on input.
So "\n" is the appropriate choice for "DOS-based" systems.

>debug file
-rcx
CX 000A
:
-d100 la
137B:0100  61 62 63 0D 0A 64 65 66-0D 0A                     abc..def.
+.
-q

>perl -le"while (<>) { print(unpack('H*', $_)) }" file
6162630a
6465660a
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