regex - Shell script linux, validating integer -

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this code check if character integer or not (i think). i'm trying understand means, mean... each part of line, checking grep man pages, it's difficult me. found on internet. if explain me part of grep... means each thing put there:

echo $character | grep -eq '^(\+|-)?[0-9]+$'

thanks people!!!

analyse regex:

'^(\+|-)?[0-9]+$'  ^ - line start (\+|-)? - optional + or - sign @ start [0-9]+ - 1 or more digits $ - line end

overall matches strings +123 or -98765 or 9

here -e extended regex support , -q quiet in grep command.

ps: btw don't need grep check , can directly in pure bash:

re='^(\+|-)?[0-9]+$' [[ "$character" =~ $re ]] && echo "its integer"

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