Learning the bash Shell 3rd Edition
ThefirstthingusersoftheUNIXorLinuxoperatingsystemscomefacetofacewithistheshell."Shell"istheUNIXtermforauserinterfacetothesystem—somethingthatletsyoucommunicatewiththecomputerviathekeyboardandthedisplay.Shellsarejustseparateprogramsthatencapsulatethe