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Full Discussion: Need advise/tip if there is more efficient way of doing this cut/paste/awk after changing a field
Top Forums UNIX for Beginners Questions & Answers Need advise/tip if there is more efficient way of doing this cut/paste/awk after changing a field Post 303044636 by MadeInGermany on Friday 28th of February 2020 12:21:43 PM
Old 02-28-2020
A more detailed explanation follows.
The main awk code runs for each input line.
!a[$0]++ is ultra-condensed, quick and dirty.
A bit more explicit is !($0 in A) { A[$0]; print }:
If not $0 in array A (A[$0] not defined) then define A[$0] (no A[$0]=value needed here) and print $0.
The array A is associative (string-addressed). So if the same $0 will occur in another input line it will see a defined A[$0] and won't print.
If there is a pre-condition and no { action code } following then the default for a true condition is { print }, and print without arguments defaults to print $0.

Now to the quick and dirty !A[$0]++:
Define A[$0] with value 0 if undefined, if the negated value is non-zero (true) then default-print. Also post-increment A[$0].
If the same $0 will occur then the A[$0] value will be 1, negated 0 (false), won't print, but post-incremented.
If the same $0 will occur then the A[$0] value will be 2, negated 0 (false), won't print, but post-incremented.
...
This User Gave Thanks to MadeInGermany For This Post:
RavinderSingh13
 

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LEARN ABOUT DEBIAN

undertaker

D:(1)								   User Commands							     D:(1)

NAME

       D: - find defects in conditinal C code

SYNOPSIS

       undertaker [OPTIONS] <file..>

DESCRIPTION

       I: undertaker v1.1+179-2bb9f3f-dirty `undertaker' analyzes conditional C code with #ifdefs.

OPTIONS

       -V     print version information

       -v     increase the log level (more verbose)

       -q     decrease the log level (less verbose)

       -m     specify the model(s) (directory or file)

       -M     specify the main model

       -w     specify a whitelist

       -b     specify a worklist (batch mode)

       -t     specify count of parallel processes

       -I     add an include path for #include directives

       -j     specify the jobs which should be done
	      dead
	       dead/undead file analysis (default)
	      coverage
	       coverage file analysis
	      cpppc
	       CPP Preconditions for whole file
	      blockpc: Block precondition (format: <file>:<line>
	       <column>)
	      symbolpc
	       Symbol precondition (format <symbol>)
	      checkexpr
	       Find a configuration that satisfies expression
	      interesting
	       Find related items (negated items are not in the model)

   Coverage Options:
       -O: specify the output mode of generated configurations

	      kconfig
	       generated partial kconfig configuration (default)
	      stdout
	       print on stdout the found configurations
	      cpp
	       print on stdout cpp -D command line arguments
	      exec:cmd
	       pipe file for every configuration to cmd
	      model
	       print all options which are in the configuration space
	      all
	       dump every assigned symbol (both items and code blocks)

       -C: specify coverage algorithm

       simple
	      - relative simple and fast algorithm (default)

       min    - slow but generates less configuration sets

   Specifying Files:
	      You  can	specify  one or many files (the format is according to the job (-j) which should be done. If you specify - as file, under-
	      taker will load models and whitelist and read files from stdin (interactive).

       please specify a file to scan or a worklist

       `undertaker' analyzes conditional C code with #ifdefs.

       Usage: undertaker [OPTIONS] <file..>

       -V     print version information

       -v     increase the log level (more verbose)

       -q     decrease the log level (less verbose)

       -m     specify the model(s) (directory or file)

       -M     specify the main model

       -w     specify a whitelist

       -b     specify a worklist (batch mode)

       -t     specify count of parallel processes

       -I     add an include path for #include directives

       -j     specify the jobs which should be done
	      dead
	       dead/undead file analysis (default)
	      coverage
	       coverage file analysis
	      cpppc
	       CPP Preconditions for whole file
	      blockpc: Block precondition (format: <file>:<line>
	       <column>)
	      symbolpc
	       Symbol precondition (format <symbol>)
	      checkexpr
	       Find a configuration that satisfies expression
	      interesting
	       Find related items (negated items are not in the model)

   Coverage Options:
       -O: specify the output mode of generated configurations

	      kconfig
	       generated partial kconfig configuration (default)
	      stdout
	       print on stdout the found configurations
	      cpp
	       print on stdout cpp -D command line arguments
	      exec:cmd
	       pipe file for every configuration to cmd
	      model
	       print all options which are in the configuration space
	      all
	       dump every assigned symbol (both items and code blocks)

       -C: specify coverage algorithm

       simple
	      - relative simple and fast algorithm (default)

       min    - slow but generates less configuration sets

   Specifying Files:
	      You can specify one or many files (the format is according to the job (-j) which should be done. If you specify -  as  file,  under-
	      taker will load models and whitelist and read files from stdin (interactive).

AUTHOR

       Written by the VAMOS team <URL:http://vamos.informatik.uni-erlangen.de>

REPORTING BUGS

       Report bugs to <vamos-dev@i4.informatik.uni-erlangen.de>.

SEE ALSO

       undertaker(1) undertaker-kconfigdump(1), undertaker-linux-tree(1).

D
: undertaker v1.1+179-2bb9f3f-dirty				   December 2011							     D:(1)
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