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Thread: assigning a variable an integer value from a string

  1. #1
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    Feb 2013
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    27

    assigning a variable an integer value from a string

    Hello I have some confusion.

    Code:
    wc -l ${list[$y]} | a= cut -d ' ' -f1a=$a+0
    echo "$a --test a"
    when I do this I am suppose to get a value for the variable a. And before this code I wrote typeset -i a=0

    yet when I'm suppose to get a certain value I;'m always getting 0. Does anyone know why?
    Thanks

    edit* list array contains files. the wc command works because it lists the number of lines plus the file name but when I use cut and get the first number and assign it to a i'm still getting 0.

  2. #2
    Join Date
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    Re: assigning a variable an integer value from a string

    Hi

    I'm not entirely sure if this is you want to do, but if you want to set 'a' with how many lines has a file, you can do this:
    Code:
    a=$(wc -l file.txt | cut -c1)
    Let us know how it goes.
    Regards.

  3. #3
    Join Date
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    Re: assigning a variable an integer value from a string

    My gosh! Thank you so much! This is exactly what I wanted! Thank you!!
    if you could could you tell me whats wrong this the coded I wrote before

    wc -l file | a= cut -d ' ' -f1

  4. #4
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    Re: assigning a variable an integer value from a string

    Sure.

    This:
    Code:
    a= cut -d ' ' -f1
    Assign blank (null string) to 'a', and then execute the command:
    Code:
    cut -d ' ' -f1
    Thus the result of your previous line:
    Code:
    wc -l file | a= cut -d ' ' -f1
    actually returns what you want, but it print it on the standard input instead of saving it on a variable.

    The second part of your line is very similar to this construction:
    Code:
    DISPLAY=:0.1  vlc movie.mkv
    which is used to run the media player vlc on a second display, identify by ":0.1"

    Does that help?
    Regards.

  5. #5
    Join Date
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    Re: assigning a variable an integer value from a string

    Oh I think i get it now.
    So I guess in the future If I want to assign a value something I should not do it in a pipe stream I Guess? Like in the code I wrote before I was assigning 'a' a value through a command that is piped. But your command assigned a after everything was piped and the final result is obtained?

  6. #6
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    Re: assigning a variable an integer value from a string

    ahhh i created another post by mistake and don't know how to delete it.....
    Last edited by toad3000; March 6th, 2013 at 10:31 PM.

  7. #7
    Join Date
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    Re: assigning a variable an integer value from a string

    I think you got it.

    It is always helps to play with some code examples:
    Code:
    $ unset var
    $ echo $var
    
    $ echo "Hello, World."
    Hello, World.
    $ echo "Hello, World." | sed 's/Hello/Bye/'
    Bye, World.
    $ echo "Hello, World." | var= sed 's/Hello/Bye/'
    Bye, World.
    $ echo $var
    
    $ var= echo "Hello, World." | sed 's/Hello/Bye/'
    Bye, World.
    $ echo $var
    
    $ var=$(echo "Hello, World." | sed 's/Hello/Bye/')
    $ echo $var
    Bye, World.
    $
    Does that help?
    Regards.

  8. #8
    Join Date
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    Re: assigning a variable an integer value from a string

    wow thanks for those examples. I tried them and played with them a bit and I think i got the hang of it!

  9. #9
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    Re: assigning a variable an integer value from a string

    Can I make just one comment about the original problem, viz:
    Code:
    a=$(wc -l file.txt | cut -c1)
    When using wc with a filename is lists the filename, e.g:
    Code:
    $ wc -l myfile
    45 myfile
    $
    But when it is used on the standard input, no filenames are listed:
    Code:
    $ wc -l < myfile
    45 
    $
    thus simplifying any code that has to count lines from:
    Code:
    a=$(wc -l file.txt | awk 'print $1')
    to:
    Code:
    a=$(wc -l < file.txt)
    Just my tuppence worth.

    Andrew

  10. #10
    Join Date
    Feb 2013
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    Re: assigning a variable an integer value from a string

    cool thanks! I didn't know that. you made the code a lot simpler to read.

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