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Top Forums Shell Programming and Scripting Difference between /text/ and "text" in awk Post 302761069 by rangarasan on Friday 25th of January 2013 04:53:30 AM
Old 01-25-2013
Quote:
Originally Posted by Jotne
Why does this search give different result in awk
I do see a mix of this in the example around the net.
What to use and why?


data
Code:
1 = red
2 = green
3 = blue
4 = black

Here you are checking the exact string "/blue/" instead of "blue" with the third column.
Code:
awk '$3 == /blue/' data
"no result"

Here you are checking the exact string "blue" with the third column. If $3 have "blue ", It wont be matched with this.
Code:
awk '$3 == "blue"' data
3 = blue

Here you are checking that the string "blue" is present in the third column? If $3 have "blue ", It will be matched with this. This is pattern matching operator.

Code:
awk '$3 ~ /blue/' data
3 = blue

Here you are checking that the string "blue" is present in the third column? If $3 have "blue ", It will be matched with this. This is pattern matching operator.

Code:
awk '$3 ~ "blue"' data
3 = blue


If you want to check the exact string == opeator will be the better choice.
If you want to check the part of the string then pattern match would be better and has more variety of options and more powerful.

Cheers,
RangaSmilie
 

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ppmdither(1)						      General Commands Manual						      ppmdither(1)

NAME
ppmdither - ordered dither for color images SYNOPSIS
ppmdither [-dim power] [-red shades] [-green shades] [-blue shades] [ppmfile] DESCRIPTION
Reads a portable pixmap as input, and applies dithering to it to reduce the number of colors used down to the specified number of shades for each primary. The default number of shades is red=5, green=9, blue=5, for a total of 225 colors. To convert the image to a binary rgb format suitable for color printers, use -red 2 -green 2 -blue 2. OPTIONS
-dim power The size of the dithering matrix. The dithering matrix is a square whose dimension is a power of 2. power is that power of 2. The default is 4, for a 16 by 16 matrix. -red shades The number of red shades to be used, including black; minimum of 2. -green shades The number of green shades to be used, including black; minimum of 2. -blue shades The number of blue shades to be used, including black; minimum of 2. SEE ALSO
pnmdepth(1), ppmquant(1), ppm(5) AUTHOR
Copyright (C) 1991 by Christos Zoulas. 14 July 1991 ppmdither(1)
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