linux – grep, pgrep, egrep, fgrep の違いは何ですか? https://code-404.net/linux-grep-pgrep-egrep-fgrep-%e3%81%ae%e9%81%95%e3%81%84%e3%81%af%e4%bd%95%e3%81%a7%e3%81%99%e3%81%8b/