This code is for check if a character is a integer or not (i think). I'm trying to understand what this means, I mean... each part of that line, checking the GREP man pages, but it's really difficult for me. I found it on the internet. If anyone could explain me the part of the grep... what means each thing put there:
echo $character | grep -Eq '^(\+|-)?[0-9]+$'
Thanks people!!!
Analyse this regex:
'^(\+|-)?[0-9]+$'
^ - Line Start
(\+|-)? - Optional + or - sign at start
[0-9]+ - One or more digits
$ - Line End
Overall it matches strings like +123 or -98765 or just 9
Here -E is for extended regex support and -q is for quiet in grep command.
PS: btw you don't need grep for this check and can do this directly in pure bash:
re='^(\+|-)?[0-9]+$'
[[ "$character" =~ $re ]] && echo "its an integer"
I like this cheat sheet for regex:
http://www.cheatography.com/davechild/cheat-sheets/regular-expressions/
It is very useful, you could easily analyze the
'^(+|-)?[0-9]+$'
as
so it accepts like: -312353243 or +1243 or 5678
but do not accept: 3 456 or 6.789 or 56$ (as dollar sign).
