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Top Forums UNIX for Beginners Questions & Answers Find matched pattern and print all based on certain conditions Post 303039510 by bunny_merah19 on Tuesday 8th of October 2019 10:43:06 AM
Old 10-08-2019
Quote:
Originally Posted by RudiC
Well, yes, I noticed the necessary removal of $20. So NF-- would remove it (if it is the last field). What is the trailing NF for?

--> I have found ways of removing the last column here in this link:
text processing - How to delete the last column of a file in Linux - Unix & Linux Stack Exchange

Code:
awk 'NF{NF-=1};1' <in >out
or:

awk 'NF{NF--};1' <in >out
or:

awk 'NF{--NF};1' <in >out
Although this looks like voodoo, it works. There are three parts to each of these awk commands.

The first is NF, which is a precondition for the second part. NF is a variable containing the number of fields in a line. In AWK, things are true if they're not 0 or empty string "". Hence, the second part (where NF is decremented) only happens if NF is not 0.

The second part (either NF-=1 NF-- or --NF) is just subtracting one from the NF variable. This prevent the last field from being printed, because when you change a field (removing the last field in this case), awk re-construct $0, concatenate all fields separated by space by default. $0 didn't contain the last field anymore.

The final part is 1. It's not magical, it's just used as a expression that means true. If an awk expression evaluates to true without any associated action, awk default action is print $0.

And, why $20 when your entire file has only 9 fields per line consistently?
-> My real data has more than that. The one that i put here just a sample. The real data quite long and messy Smilie

And - as I see now - why the NR>2 condition? You normally use this to eliminate e.g. headers. But your file seems to have valid data in lines 1 and 2?
-> I do have 2 lines header in my real data that need to be omitted. Smilie
 

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IGAWK(1)							 Utility Commands							  IGAWK(1)

NAME
igawk - gawk with include files SYNOPSIS
igawk [ all gawk options ] -f program-file [ -- ] file ... igawk [ all gawk options ] [ -- ] program-text file ... DESCRIPTION
Igawk is a simple shell script that adds the ability to have ``include files'' to gawk(1). AWK programs for igawk are the same as for gawk, except that, in addition, you may have lines like @include getopt.awk in your program to include the file getopt.awk from either the current directory or one of the other directories in the search path. OPTIONS
See gawk(1) for a full description of the AWK language and the options that gawk supports. EXAMPLES
cat << EOF > test.awk @include getopt.awk BEGIN { while (getopt(ARGC, ARGV, "am:q") != -1) ... } EOF igawk -f test.awk SEE ALSO
gawk(1) Effective AWK Programming, Edition 1.0, published by the Free Software Foundation, 1995. AUTHOR
Arnold Robbins (arnold@skeeve.com). Free Software Foundation Nov 3 1999 IGAWK(1)
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