This is a perl one-liner doing just what you want: 
$ echo 'ACATCACCTCCCACAACGAGGACTACACCATCGTGGAACA
> ACATCACCTCCCACAACGAGGACTACACCATCGTGGAACA
> ACATCACCTCCCACAACGAGGACTACACCATCGTGGAACA
> ACATCACCTCCCACAACGAGGACTACACCATCGTGGAACA
> ACATCACCTCCCACAACGAGGACTACACCATCGTGGAACA
> ACATCACCTCCCACAACGAGGACTACACCATCGTGGAACA
> ACATCACCTCCCACAACGAGGACTACACCATCGTGGAACA
> ACATCACCTCCCACAACGAGGACTACACCATCGTGGAACA
> ACATCACCTCCCACAACGAGGACTACACCATCGTGGAACA
> ACATCACCTCCCACAACGAGGACTACACCATCGTGGAACA
> ACATCACCTCCCACAACGAGGACTACACCATCGTGGAACA
> ACATCACCTCCCACAACGAGGACTACACCATCGTGGAACA
> ACATCACCTCCCACAACGAGGACTACACCATCGTGGAACA' | perl -nE 'say substr($_,
+ 10, 1);'
C
C
C
C
C
C
C
C
C
C
C
C
C

[download]
Check, though, that 10 is the right second parameter for substr, you may have to change it depending on which character you want exactly.

In reply to Re: Faster and more efficient way to read a file vertically by Laurent_R
in thread Faster and more efficient way to read a file vertically by Anonymous Monk

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