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Ping Phoenix

Discussion in 'Linux / Unix Discussion' started by ffreeloader, Oct 13, 2005.

  1. ffreeloader

    ffreeloader Terabyte Poster

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    In the following output from a bash shell I get some behavior I don't quite understand. The variable $a is a="^H^H" which is actually two Control-H's. (To insert two visible Control-H's you have to hit Control-V first, continue to hold down the Control key and hit the H, then the V and then the H once more.) The Control-H character in a bash shell is a "destructive" backspace, i.e. same as the backspace key.

    Can you, Phoenix, or anyone else, explain why I get the output I do from the following? I don't understand why the number of empty spaces before the trailing " makes a difference in the output.

    While the formatting here doesn't show the spaces in the output and input very well, there are actual empty spaces in the output.
     
    Certifications: MCSE, MCDBA, CCNA, A+
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  2. Phoenix
    Honorary Member

    Phoenix 53656e696f7220 4d6f64

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    i honestly couldnt tell you freddy mate, you probably know more about bash than me, i'll ask around though mate
    let us know if you find out in the mean time!
     
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  3. ffreeloader

    ffreeloader Terabyte Poster

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    Well, I was sorta counting on you. I figured if there was anyone around who would know the bash shell pretty well it would be you, seeing how you're a Gentoo guy. We all know that Gentoo guys are the real geeks so.... :(
     
    Certifications: MCSE, MCDBA, CCNA, A+
    WIP: LPIC 1
  4. d-Faktor
    Honorary Member

    d-Faktor R.I.P - gone but never forgotten.

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    what is the output when you put braces around your variable letter, like so: ${a}
     
  5. ffreeloader

    ffreeloader Terabyte Poster

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    d-Faktor,

    What follows is starts with 1 space and ends up with thee spaces before the trailing ". Expansion doesn't really seem to make much difference.

     
    Certifications: MCSE, MCDBA, CCNA, A+
    WIP: LPIC 1
  6. d-Faktor
    Honorary Member

    d-Faktor R.I.P - gone but never forgotten.

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    ${a}, not {$a}
    you enclose your variable, so that any other characters are not taken into consideration when echoing a double quoted line.
    i'm not saying it will change anything for your example, but that's the way i've always used it.
     
  7. ffreeloader

    ffreeloader Terabyte Poster

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    d-Faktor,

    Welll, I see my dyslexia is acting up again.... :oops:

    I got the same output when I actually used the correct expansion syntax, ${a}, as I did with the original syntax. No change whatsoever.
     
    Certifications: MCSE, MCDBA, CCNA, A+
    WIP: LPIC 1

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