In a Linux environment mongoD (and probably the other binaries) treats the CR/LF as a CR appended to the last argument, which doesn't work.

mongod --oplogSize 8192 using CR/LF results in:
Error parsing command line: in option 'oplogSize': invalid option value

$ hexdump -C /tmp/foo
00000000  6d 6f 6e 67 6f 64 20 2d  2d 6f 70 6c 6f 67 53 69  |mongod --oplogSi|
00000010  7a 65 20 38 31 39 32 0d  0a                       |ze 8192..|
00000019