如何删除与模式匹配的特定数量的随机行

Question

I have an svg file with a grid of dots represented by lines that have the word use in them. I would like to delete a specific number of random lines matching that use pattern, then save a new version of the file. This answer was very close.

So it will be a combination of this (delete one random line in a specific range):

sed -i '.svg' $((9 + RANDOM % 579))d /filename.svg 

and this (delete all lines matching pattern use ):

sed -i '.svg' /use/d /filename.svg

In other words, the logic would go something like this:

sed -i delete 'x' number of RANDOM lines matching 'use' from 'input.svg' and save to 'output.svg'

I'm running these commands from Terminal on a Mac and am inexperienced with syntax so formatting the command for that would be ideal.

Answer 1

Delete each line containing "use" with a probability of 10%:

awk '!/use/ || rand() > 0.10' file

Randomly delete exactly one line containing "use":

awk -v n="$(( RANDOM % $(grep -c "use" file) ))" '!/use/ || n-- != 0' file

Here's an example invocation:

$ cat file
some string
a line containing "use"
another use-ful line
more random data

$ awk -v n="$(( RANDOM % $(grep -c "use" file) ))" '!/use/ || n-- != 0' file
some string
another use-ful line
more random data

One of the lines containing use was removed.

Answer 2

This might work for you: (GNU sed & sort):

sed -n '/\<use\>/=' file | sort -r | head -5 | sed 's/$/d/' | sed -i.bak -f - file

Extract the line numbers of the lines containing the word use from the file. Randomly sort those line numbers then take the first say 5 and build a sed script to delete them from the original file.