(runningwater认领)
Linux Terminal: Seeing the unseen characters with cat!
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Sometimes a program or software don’t start for a syntax error, and if you check the files there is nothing wrong..apparently.
There are a lot of characters that usually are not printed if you use a normal text editor, but you can easily check if they are present with your terminal and the command cat.

As first thing let’s create a simple text file with these special characters, open a terminal and run the command:

    printf 'testing\012\011\011testing\014\010\012more testing\012\011\000\013\000even more testing\012\011\011\011\012' > /tmp/testing.txt

Now if you open the file with an editor you’ll have different results.
A simple cat will show:

    $ cat /tmp/testing.txt 
    testing
    		testing
     
    more testing
     
    even more testing
    
While if you open it with nano or vim you’ll see :

    testing
                testing^L^H

    more testing
        ^@^K^@even more testing

Now we can see some options of cat to print special characters.

1) Use cat -T to display TAB characters as ^I

    cat -T /tmp/testing.txt
    testing
    ^I^Itesting
     
    more testing
    ^I
      even more testing
    ^I^I^I

2) Use cat -E to display $ at end of each line

    $ cat -E /tmp/testing.txt
    testing$
    		testing
      $
    more testing$
     
    even more testing$
    			$

3) Use a simple cat -A to show up all the invisible characters:

    $ cat -A /tmp/testing.txt
    testing$
    ^I^Itesting^L^H$
    more testing$
    ^I^@^K^@even more testing$
    ^I^I^I$

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via: http://linuxaria.com/pills/linux-terminal-seeing-the-unseen-characters-with-cat?lang=en#more-7645

本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译，[Linux中国](http://linux.cn/) 荣誉推出

译者：[runningwater](https://github.com/runningwater) 校对：[校对者ID](https://github.com/校对者ID)

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