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Full Discussion: nawk code explanation
Top Forums Shell Programming and Scripting nawk code explanation Post 302322649 by vidyadhar85 on Thursday 4th of June 2009 09:22:15 AM
Old 06-04-2009
Quote:
Originally Posted by aoussenko
Hi
I have a line/command which greps certain pattern ([435]) from the file and 22 lines AFTER that:

nawk '/\[435\]/{c=22}c&&c--' input_file

Can somebody explain the coding in this command (what " c&&c-- " does)? and how to modify this command to output 22 lines BEFORE this pattern ([435]) Thanks a lot -A
in your code first it search for pattern if its found it sets c to 22
then it decrement the value of c untill 22&&0 becomes 0 and exit


you can use this awk to print either above or below or both lines from pattern
Code:
awk 'c-->0;$0~s{if(b)for(c=b+1;c>1;c--)print r[(NR-c+1)%b];print;c=a}b{r[NR%b]=$0}' b=3 a=5 s="pattern" filename

b-->no of lines above the pattern
a-->no of line below the pattern
 

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LEARN ABOUT REDHAT

gllinestipple

GLLINESTIPPLE(3G)														 GLLINESTIPPLE(3G)

NAME

       glLineStipple - specify the line stipple pattern

C SPECIFICATION

       void glLineStipple( GLint factor,
			   GLushort pattern )

PARAMETERS

       factor	Specifies  a  multiplier  for  each bit in the line stipple pattern.  If factor is 3, for example, each bit in the pattern is used
		three times before the next bit in the pattern is used.  factor is clamped to the range [1, 256] and defaults to 1.

       pattern	Specifies a 16-bit integer whose bit pattern determines which fragments of a line will be drawn when the line is rasterized.   Bit
		zero is used first; the default pattern is all 1's.

DESCRIPTION

       Line  stippling masks out certain fragments produced by rasterization; those fragments will not be drawn.  The masking is achieved by using
       three parameters: the 16-bit line stipple pattern pattern, the repeat count factor, and an integer stipple counter s.

       Counter s is reset to 0 whenever glBegin is called, and before each line segment of a glBegin(GL_LINES)/glEnd sequence is generated.  It is
       incremented after each fragment of a unit width aliased line segment is generated, or after each i fragments of an i width line segment are
       generated.  The i fragments associated with count s are masked out if

							       pattern bit (s/factor)mod16

       is 0, otherwise these fragments are sent to the frame buffer.  Bit zero of pattern is the least significant bit.

       Antialiased lines are treated as a sequence of 1xwidth rectangles for purposes of stippling.  Whether  rectagle	s  is  rasterized  or  not
       depends on the fragment rule described for aliased lines, counting rectangles rather than groups of fragments.

       To enable and disable line stippling, call glEnable and glDisable with argument GL_LINE_STIPPLE.  When enabled, the line stipple pattern is
       applied as described above.  When disabled, it is as if the pattern were all 1's.  Initially, line stippling is disabled.

ERRORS

       GL_INVALID_OPERATION is generated if glLineStipple is executed between the execution of glBegin and the corresponding execution of glEnd.

ASSOCIATED GETS

       glGet with argument GL_LINE_STIPPLE_PATTERN
       glGet with argument GL_LINE_STIPPLE_REPEAT
       glIsEnabled with argument GL_LINE_STIPPLE

SEE ALSO

       glLineWidth(3G), glPolygonStipple(3G)

																 GLLINESTIPPLE(3G)
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