Script to process a list of items and uncomment lines with that item in a second file Post: 303042968

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Top Forums Shell Programming and Scripting Script to process a list of items and uncomment lines with that item in a second file Post 303042968 by LMHmedchem on Tuesday 14th of January 2020 12:15:18 PM

01-14-2020

Registered User

Quote:

Originally Posted by RudiC

Nice approach indeed!
Could be curtailed to

Code:

sed -r "/'($(paste -sd\| file2))'/s/^C//" file1

, including the item list file as well.

I went with this method inserted into a script. It worked well (and very quickly) the first time I tried it, but there was no output the second time. I will have to investigate what I did there.

I also made a second try before there were any responses here. This ended up looking more like the code posted by MadeInGermany where I read in the file to be modified and stored it in an array. I then did a double loop with the outside loop being my list file and the inside loop being the array with the file to be modified. Each item in the list was searched against the lines in the array. If a match was found, the array element was modified to remove the comment and then there was a break in the inner loop. The modified array was printed at the end. This approach means that each file is read in once and the output was written once, instead of once for each list item.

It seems to me that sed must be doing more or less the same thing under the hood. Every list item must be checked against every item in the file to be modified, at least until a match is found. I wasn't able to rationalize if it was more efficient to have one or the other file be the inner loop. The only approach I could think of that would be faster would be to identify the 'Gmax" value on each line of the file to be modified and then loop up that value in a map holding the list. That would, however, involve much more significant parsing of the lines to extract the 'Gmax' value. It is very nice to have a glob match, especially when there isn't a clear and consistent delimiter. If the list was the inner loop, you could delete each array element when a match was found and thus shorten the search as the process continues but deleting and shifting around array elements also takes resources.

Does anyone know what sed is doing to achieve the result so quickly? Is it mainly that is is using compiled code?

LMHmedchem

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dmenu

DMENU(1)						      General Commands Manual							  DMENU(1)

NAME

       dmenu - dynamic menu

SYNOPSIS

       dmenu [-b] [-i] [-l lines] [-m monitor] [-p prompt] [-fn font] [-nb color] [-nf color] [-sb color] [-sf color] [-v]

       dmenu_run ...

       dmenu_path

DESCRIPTION

       dmenu is a dynamic menu for X, originally designed for dwm(1).  It manages huge numbers of user-defined menu items efficiently.

       dmenu reads a list of newline-separated items from standard input and creates a menu.  When the user selects an item or enters any text and
       presses Return, their choice is printed to standard output and dmenu terminates.

       dmenu_run is a dmenu script used by dwm which lists programs in the user's PATH and executes the selected item.

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OPTIONS

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       -i     dmenu matches menu items case insensitively.

       -l lines
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       -m monitor
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       -p prompt
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       -nb color
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       -sf color
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USAGE

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       Down, Home/End), the following keys are recognized:

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       Control-y
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SEE ALSO

       dwm(1)

								    dmenu-4.2.1 							  DMENU(1)