Combine awk commands into one Post: 302979708

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Top Forums Shell Programming and Scripting Combine awk commands into one Post 302979708 by bakunin on Thursday 18th of August 2016 05:56:08 AM

08-18-2016

Registered User

As a general remark about one-liners: one-liners reduce readability and understandability. Their advantage is that they can be fastly written.

Given that you are unable to modify your already existing one-liners (which i take as a hint that you are not completely understanding them already) i suggest that it is a bad idea to combine these to an even more complex construct which you are bound to understand even less.

It is of course always possible to rely on us (or other people like us) to provide modifications as the code will need to be modified but, honestly: do you really want to preside over an environment where you do not understand what is going on? It might be me but i for my part would have a very bad feeling being in such a position.

It is in your own best interest if you rely on us only if you need an explanation to further your understanding but not to write or modify your productive code. Whatever you use finally you should be able to produce on your own and you should write it in a way that you are able to understand its inner workings.

Btw., over time i found that restricting my written code to 80 characters per line with only select few exceptions (for instance definitions of string constants) makes my code more readable and better overall. The reason is that a line containing more than 80 characters is most likely badly formed and should be rewritten in a more conclusive manner anyways. This in most cases means i reformat one-liners to their long form.

Here is an example where i filter out comments and whitespace from an input file before processing:

Code:

sed 's/#.*//;s/^[ 	]*//;s/[ 	]*$//;/^$/d' "$fCmd" | while read chCmd ; do
     .....
done

Going over that code i modified it to:

Code:

sed 's/#.*//
     s/^[ 	]*//
     s/[ 	]*$//
     /^$/d' "$fCmd" |\
while read chCmd ; do
     .....
done

I'd say the second variant gives you a much cleaner and easier to grasp impression of what is going on than the first.

I hope this helps.

bakunin

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LEARN ABOUT CENTOS

ppi::token::comment

PPI::Token::Comment(3)					User Contributed Perl Documentation				    PPI::Token::Comment(3)

NAME

       PPI::Token::Comment - A comment in Perl source code

INHERITANCE

	 PPI::Token::Comment
	 isa PPI::Token
	     isa PPI::Element

SYNOPSIS

	 # This is a PPI::Token::Comment

	 print "Hello World!"; # So it this

	 $string =~ s/ foo  # This, unfortunately, is not :(
	       bar
	       /w;

DESCRIPTION

       In PPI, comments are represented by "PPI::Token::Comment" objects.

       These come in two flavours, line comment and inline comments.

       A "line comment" is a comment that stands on its own line. These comments hold their own newline and whitespace (both leading and trailing)
       as part of the one "PPI::Token::Comment" object.

       An inline comment is a comment that appears after some code, and continues to the end of the line. This does not include whitespace, and
       the terminating newlines is considered a separate PPI::Token::Whitespace token.

       This is largely a convenience, simplifying a lot of normal code relating to the common things people do with comments.

       Most commonly, it means when you "prune" or "delete" a comment, a line comment disappears taking the entire line with it, and an inline
       comment is removed from the inside of the line, allowing the newline to drop back onto the end of the code, as you would expect.

       It also means you can move comments around in blocks much more easily.

       For now, this is a suitably handy way to do things. However, I do reserve the right to change my mind on this one if it gets dangerously
       anachronistic somewhere down the line.

METHODS

       Only very limited methods are available, beyond those provided by our parent PPI::Token and PPI::Element classes.

   line
       The "line" accessor returns true if the "PPI::Token::Comment" is a line comment, or false if it is an inline comment.

SUPPORT

       See the support section in the main module.

AUTHOR

       Adam Kennedy <adamk@cpan.org>

COPYRIGHT

       Copyright 2001 - 2011 Adam Kennedy.

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

       The full text of the license can be found in the LICENSE file included with this module.

perl v5.16.3							    2011-02-26						    PPI::Token::Comment(3)

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