리눅스 쉘 스크립트 학습 - 입력값이 숫자인지 확인하는 스크립트

isNumber.sh

• ^ : Beginning. Mtaches the beginning of the string, or the beginning of a line if the multiline flag (m) is enabled.
• [] : character set. Match any character in the set
• "+" : Quantifier. Match 1 or more of the preceding token.
• $ : End. Matches the end of the string, or the end of a line if the multiline flag (m) is enabled.