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Thread: BASH skipping values in loop

  1. #1
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    Question BASH skipping values in loop

    Hello Linux experts,

    I am attempting to extract segments of a large output file and put each segment into its own file.

    My script:
    Code:
    #!/bin/bash
    
    #pull out structures from Gaussian09 Scan.
    
    for ((x=43, y=44; x<1200, y<1200; x+=43, y+=46))
    do
     grep -A 43 'Z-MATRIX' structures.out | head -$x | tail -39 > tmp_Zmatrix
     CHI="`grep '11     11  C' tmp_Zmatrix | awk '{print $11}' | sed 's/.$//g'`"
     EPSILON="`grep '15     15  C' tmp_Zmatrix | awk '{print $11}' | sed 's/.$//g'`"
     ZETA="`grep '32     32  O' tmp_Zmatrix | awk '{print $11}' | sed 's/.$//g'`"
     echo $CHI $EPSILON $ZETA
     echo 39 > ppa18_chi$CHI\_epsilon$EPSILON\_zeta$ZETA.xyz
     echo ppa18_chi$CHI\_epsilon$EPSILON\_zeta$ZETA >> ppa18_chi$CHI\_epsilon$EPSILON\_zeta$ZETA.xyz
     grep -A 44 'Z-Matrix orientation:' structures.out | head -$y | tail -39 | awk '{print $2, $4, $5, $6}' | sed -e 's/^1 /H /g' -e 's/^6/C/g' -e 's/^7/N/g' -e 's/^8/O/g' -e 's/^15/P/g' >> ppa18_chi$CHI\_epsilon$EPSILON\_zeta$ZETA.xyz
     rm tmp_Zmatrix
    done
    The problem, I think, is in the for loop title (something about different steps being used). I used the "echo" line as a function check. As you can see, it skips certain values (the first two columns shouldn't change):

    Code:
    62.990 179.970 -179.140
    62.990 179.970 -164.740
    62.990 179.970 -150.340
    62.990 179.970 -135.940
    62.990 179.970 -121.540
    62.990 179.970
    62.990 179.970
    62.990 179.970
    62.990 179.970 -78.340
    62.990 179.970 -63.940
    62.990 179.970 -49.540
    62.990 179.970 -35.140
    62.990 179.970 -20.740
    62.990 -6.340
    62.990 8.060
    22.460
    179.970 36.860
    179.970 51.260
    62.990 179.970 65.660
    62.990 179.970 80.060
    62.990 179.970 94.460
    62.990 179.970 108.860
    62.990 179.970 123.260
    62.990 179.970 137.660
    62.990 179.970 152.060
    62.990 179.970 166.460
    I have checked the file structures.out and the data is there, but the script isn't extracting and reporting like it should. I don't understand why it does this for some lines, and not others.

    How can I change the script to get all values to appear?

    Thanks for your expertise!
    -Dave

  2. #2
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    Re: BASH skipping values in loop

    holy crap
    advice: stop using backticks and use $() instead to capture command outputs

    how big is the file? Can you create a simplified example that bugs your loop out?
    some sample data would be cool. Either grep doesn't catch anything or awk spits out a single character which is destroyed by sed down the road.

  3. #3
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    Red face Re: BASH skipping values in loop

    Hi Vaphell!

    thanks for replying! I actually fixed that problem a few hours later. Unfortunately, I ran into another one. In Perl, I can add numbers to a variable rather easily. However the same doesn't appear to be true in Bash.

    I just want to add 360 to ZETA if it is less than 0, so all my numbers will be positive. I've attempted to do this with an "if" conditional in line 12. I've just included the important part:

    Code:
    ...
     ZETA="`grep '32     32  O' tmp_Zmatrix | awk '{print $11}' | sed 's/.$//g'`"
    	if ["$ZETA" -lt 0]; then
    		ZETA=$(($ZETA + 360))
    	fi
     ...
    I've tried many different ways of adding 360 to something, this is so easy, it should work!!!

    thanks for your time,
    -Dave

  4. #4
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    Re: BASH skipping values in loop

    drop if and go with modulo arithmetic
    Code:
    $ x=0; echo $(((x+360)%360))
    0
    $ x=-1; echo $(((x+360)%360))
    359
    $ x=700; echo $(((x+360)%360))
    340
    bash arithmetic works only with integers though

    EDIT:
    another way: echo the equation and pipe it to bc
    Code:
    $ x=-0.00001; echo "($x+360)%360" | bc
    359.99999
    $ x=-94.2; echo "($x+3600)%360" | bc
    265.8
    Last edited by Vaphell; September 13th, 2011 at 10:49 PM.

  5. #5
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    Re: BASH skipping values in loop

    http://mywiki.wooledge.org/ArithmeticExpression

    Oh, and learn more about awk, you can replace all the grep .. | sed .. | awk .. commands with a one awk. I'm not very good with awk, but intead of grep foo | awk '{print $1}' you can use awk '/foo/{print $1}'

    Also check out the links from my signature.

  6. #6
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    Re: BASH skipping values in loop

    Hi sisco311 and Vaphell!

    thank you so much!! Vaphell, your suggestion worked beautifully.

    sisco311, I will improve the script once I get the time. I have to modify the other 2 variables now, and get the output from this into the supercomputing cluster.

    THANKS SO MUCH!!!

    Code:
    #!/bin/bash
    
    #pull out structures from Gaussian09 Scan.
    
    grep -A 41 'Z-MATRIX (ANGSTROMS AND DEGREES)' structures.out > zmat_list.txt
    for ((x=44, y=44; x<1175, y<1200; x+=43, y+=46))
    do
     head -$x zmat_list.txt | tail -39 > tmp_Zmatrix
     CHI="`grep '11     11  C' tmp_Zmatrix | awk '{print $11}' | sed 's/.$//g'`"
     EPSILON="`grep '15     15  C' tmp_Zmatrix | awk '{print $11}' | sed 's/.$//g'`"
     FALSEZETA="`grep '32     32  O' tmp_Zmatrix | awk '{print $11}' | sed 's/.$//g'`"
            ZETA="`echo "($FALSEZETA+360)%360" | bc`"
     echo $CHI $EPSILON $ZETA
     echo 39 > ppa18_X$CHI\_E$EPSILON\_Z$ZETA.xyz
     echo ppa18_X$CHI\_E$EPSILON\_Z$ZETA >> ppa18_X$CHI\_E$EPSILON\_Z$ZETA.xyz
     grep -A 44 'Z-Matrix orientation:' structures.out | head -$y | tail -39 | awk '{print $2, $4, $5, $6}' | sed -e 's/^1 /H /g' -e 's/^6/C/g' -e 's/^7/N/g' -e 's/^8/O/g' -e 's/^15/P/g' >> ppa18_X$CHI\_E$EPSILON\_Z$ZETA.xyz
     rm tmp_Zmatrix
    done

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