Questions[wc](ubuntu)

I want to run wc -l and use the result in an arithmetic expansion. In other words, I want to do something like this:

wc -l (now somehow pipe/pass the result of this to) $((2 + result of wc command))

How can I do this?

Context

In my ~/Pictures directory, I have multiple files named "Screenshot from YYYY-MM-DD hh-mm-ss.png", as well as other files. I want to keep all files that are not Screenshots, and only a specified number of Screenshot pictures, based on how recent they were. I want to basically only keep the last 3 most recent Screenshots I have, and delete all the rest.

So here is what I have so far:

ls | grep "Screenshot *" | sort -r | wc -l

What I then wanted to do was to subtract 3 from wc -l, which would then allow me to use tail to list all the files that are not the first 3, and then just delete them.

I select some text and copy it using Ctrl + c. Now the text is in the system clipboard. I can paste this code using Ctrl + v in a file and run wc for the file to check the count of characters, lines and words.

But if I want to count the characters of the text in the clipboard without saving this in a file, is there a solution?

I want to count the number of different name in a text file of this presentation:

2008 girl Avah
2009 girl Avah
2008 girl Carleigh
2011 girl Kenley
2012 boy Joseph
2013 boy Joseph
2014 boy Isaac
2014 boy Brandon

So basically I want to skip the duplicate and have as an answer 6. I tried with awk to access only the third column but I can't get it to print the number of lines.

I'm working on a Bash script and the length of the string contained in a certain variable is one of my conditions. The current string is W5u7TBTzF17GGFV8DBJHvgAAAAI. Initially I've count the string length by the help of wc -c:

$ VAR='W5u7TBTzF17GGFV8DBJHvgAAAAI'; echo "$VAR" | wc -c
28

But my script condition [[ ${#VAR} -eq 28 ]] never pass. Then I decided to count the characters on by one. Indeed the string length is 27 characters, also the value of ${#VAR} is 27:

$ echo "${#VAR}"
27

So I'm in wondering - where does this difference come from?

I want to count the total number of lines in all /etc files but not the files in the sub directories, so I typed: wc -l /etc/* | tail -1 and the output is like:

xxxx is a directory 
yyyy is a directory
total 1752

My question is, how can I rid of (delete) these comments, and is there a better way to do this type of count?