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George Shuklin
Asked: 2017-02-01 05:27:10 +0800 CST

How to input CRLF from keyboard in linux console

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I want to test mail relay. It requires me to send CRLF at the end of DATA.

I can use toggle CRLFin telnet, or -C option for NC. But is there a way to input CRLF from keyboard in linux terminal?

linux console keyboard-shortcuts

2 Answers

  1. Using vi, create a file having these two characters

    • vi file then i to enter input mode
    • Hit ^V followed by the decimal code of ^M:
    • ^V013 for CR
    • then save :wq since LF is automatically added by vi

    If you have it (or install it) doing

    hexdump -C file

    should show

    00000000  0d 0a                                             |..|

    Now you can copy / paste or cat that file where necessary.

    You could also prepare the file with other characters, headers that you cat one shot to your application.

    Another, way is to install dos2unix (depending on your distrib), then prepare the file as necessary (ie without the CR aka ^M), then do

    unix2dos file

    and all 0a will be converted to 0d0a

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  2. Normally I would expect you can just press enter/return but if you really need to send CRLF then you can use

    Ctrlm for CR and
    Ctrlj for LF

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