Help a newbie please with awk if else statements Post: 302244175

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Top Forums Shell Programming and Scripting Help a newbie please with awk if else statements Post 302244175 by otheus on Tuesday 7th of October 2008 11:12:07 AM

10-07-2008

Registered User

Looking at this again, I think you're confused about how awk works. Each line is compared to each pattern, in turn, and if there is a match, the "program" part (for each pattern that matches) is then run, in turn. After all input is consumed, THEN the "END" block is executed. To have one of these programs "skip" to the next line, use "next;". Further points:

1. I'm not sure what you are trying to do with the NR==1 line (you never write to new_fname). You can output to a file with "printf expr list >filename".

2. You're not using sprintf() in a meaningful way, except to avoid printing out a newline. You can just do "print $1, $38, $50", except that a newline will be appended. But I don't see why you're using it this way.

3. Instead of "END", you can have a "default" program at the end. Sometimes you have to give it an expression of "1". This way you can prepare your output and then have:

Code:

/pattern/ { program1 }
/pattern2/ { program 2 }
...
1 { print output >newfilename }

You can also put this at the beginning of the list of pattern-programs, and that way it will execute every time, regardless if a program uses "next". Here, however, you have to be sure that (1) you don't print out when there is nothing to print out, and (2) if you don't want to print out something, you empty the field.

Code:

length(output) { print output > newfilename } 

/badfield/ {  output=""; next; }
/goodfield/ { output=output "blah blah"; next; }
/other/ { output="fubar"; }
...

otheus

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LEARN ABOUT DEBIAN

regexp-assemble

REGEXP-ASSEMBLE(1p)					User Contributed Perl Documentation				       REGEXP-ASSEMBLE(1p)

NAME

       regexp-assemble - Assemble a list of regular expressions from a file

SYNOPSIS

	 regexp-assemble -abcdfinprsStTuUvw file [...]

DESCRIPTION

       Assemble a list of regular expression either from standard input or a file, using the Regexp::Assemble module.

OPTIONS

       -a   look Ahead. Insert "(?=...)" zero-width lookahead assertions in the pattern, where necessary.

       -b   Blank. Ignore blank lines.

       -c   Comment. Basic comment filtering. Strip off perl/shell comments ("s*#.*$/").

       -d   Debug. Turns on debugging output. See Regexp::Assemble for suitable values.

       -i   Indent. Print the regular expression using and indent of n to display nesting. A.k.a pretty-printing. Implies -p.

       -n   No newline. Do not print a newline after the pattern. Useful when interpolating the output into a templating system or similar.

       -p   Print. Print the pattern. This is the default, however, it is required when the -t switch is enabled (because if you want to test
	    patterns ordinarily you don't care what the the assembled pattern looks like).

       -r   Reduce. The default behaviour is to reduce the assembled pattern.  Enabling this switch causes the reduction algorithm to be switched
	    off. This can help you determine how much reduction is performed.

	      regexp-assemble pattern.file | wc
	      # versus
	      regexp-assemble -r pattern.file | wc

       -s   Statistics. Print some statistics about the assembled pattern. The output is sent to STDERR (in order to allow the generated pattern
	    to be redirected elsewhere).

       -S   Statistics only. Like -s, except that the pattern itself is not output. Useful with -d 8 to see the time taken.

       -t   Test. Test the assembled expression against the contents of a file.  Each line is read from the file and is matched against the
	    pattern.  Lines that fail to match are printed. In other words, no output is good output. In this mode of operation, error status is 1
	    in the case of a failure, 0 if all lines matched.

       -T   Time. Print statistics on the time taken to reduce and assemble the pattern. (This is merely a lazy person's synonym for "-d 8").

       -u   Unique. Carp if duplicate patterns are found.

       -U   Unroll. Transform "a+" et al into "aa*" (which may allow additional reductions).

       -v   Version. Print the version of the regexp-assemble script.

       -w   Word/Whole. When testing the contents of a file with "-t", bracket the expression with "^" and "$" in order to match the whole word or
	    line from the file.

DIAGNOSTICS

       Will print out a summary of the problem if an added pattern causes the assembly to fail.

SEE ALSO

       Regexp::Assemble

AUTHOR

       Copyright (C) 2004-2008 David Landgren. All rights reserved.

LICENSE

       This script is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

perl v5.14.2							    2012-06-30						       REGEXP-ASSEMBLE(1p)

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