... expr2Check whether either of the two expressions is truefile1 -nt file2Check whether the first file is newer than the second file (using the modification timestamp)66Chapter 3: Using the Shell 82935c03.qxd:Toolbox ... programming.Although the shell used most often with Linuxsystems is called the Bourne Again Shell (bash),other shells are available as well (such as sh, csh,ksh, tcsh, and others). In many cases, these shells,such ... Using the Shell The use of a shell command interpreter (usuallyjust called a shell) dates back to the early days of the first Unix systems. Besides its obvious use ofrunning commands, shells...