This section will describe some of the features that are common in all of the shells. The flags modify the behavior of the command, for example, while the ls command will list files in the current directory, using ls -l will modify the output so that it includes information about file size, protections, and ownership.
Arguments are the major operand of the command and are often file names, host names, or user names.
For example, cat report.txt will list out the contents of the file named report.txt. Unix is case sensitive and expects most commands to be typed in lower case. Wildcards Unix usually treats typed input literally, that is, without minimum matching. Figure 4.1 shows some examples of directory listings produced using wildcard characters. When you match a subdirectory name with a wildcard character, the contents of that directory will be listed.