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Full Discussion: Pull specific lines from long file based on formula
Top Forums Shell Programming and Scripting Pull specific lines from long file based on formula Post 302509357 by jim mcnamara on Wednesday 30th of March 2011 03:11:22 PM
Old 03-30-2011
This reads the file 100 times. If the file has 10^8 lines that will take all day.
You can embed the loop into awk, which is not super fast, but is acceptable:
Code:
limit=101
a=0
b=1
awk -v lim=$limit '
     {   
     for(n=1; n<lim; n++) 
       { 
          if(NR==a+(b*n) )
            {print $0 }
       } '  a=$a b=$b  inputfile > outputfile

 

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LEARN ABOUT DEBIAN

sla_lin_berr.f

sla_lin_berr.f(3)						      LAPACK							 sla_lin_berr.f(3)

NAME

       sla_lin_berr.f -

SYNOPSIS

   Functions/Subroutines
       subroutine sla_lin_berr (N, NZ, NRHS, RES, AYB, BERR)
	   SLA_LIN_BERR

Function/Subroutine Documentation
   subroutine sla_lin_berr (integerN, integerNZ, integerNRHS, real, dimension( n, nrhs )RES, real, dimension( n, nrhs )AYB, real, dimension( nrhs
       )BERR)
       SLA_LIN_BERR

       Purpose:

	       SLA_LIN_BERR computes componentwise relative backward error from
	       the formula
		   max(i) ( abs(R(i)) / ( abs(op(A_s))*abs(Y) + abs(B_s) )(i) )
	       where abs(Z) is the componentwise absolute value of the matrix
	       or vector Z.

       Parameters:
	   N

		     N is INTEGER
		The number of linear equations, i.e., the order of the
		matrix A.  N >= 0.

	   NZ

		     NZ is INTEGER
		We add (NZ+1)*SLAMCH( 'Safe minimum' ) to R(i) in the numerator to
		guard against spuriously zero residuals. Default value is N.

	   NRHS

		     NRHS is INTEGER
		The number of right hand sides, i.e., the number of columns
		of the matrices AYB, RES, and BERR.  NRHS >= 0.

	   RES

		     RES is REAL array, dimension (N,NRHS)
		The residual matrix, i.e., the matrix R in the relative backward
		error formula above.

	   AYB

		     AYB is REAL array, dimension (N, NRHS)
		The denominator in the relative backward error formula above, i.e.,
		the matrix abs(op(A_s))*abs(Y) + abs(B_s). The matrices A, Y, and B
		are from iterative refinement (see sla_gerfsx_extended.f).

	   BERR

		     BERR is REAL array, dimension (NRHS)
		The componentwise relative backward error from the formula above.

       Author:
	   Univ. of Tennessee

	   Univ. of California Berkeley

	   Univ. of Colorado Denver

	   NAG Ltd.

       Date:
	   November 2011

       Definition at line 102 of file sla_lin_berr.f.

Author
       Generated automatically by Doxygen for LAPACK from the source code.

Version 3.4.1							  Sun May 26 2013						 sla_lin_berr.f(3)
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