The grep command is a tool that searches for a pattern of characters in a file or input and prints the matching lines1 The egrep command is a variant of grep that supports extended regular expressions, which allow more complex and flexible pattern matching2 The more command is a filter that displays the contents of a file or input one screen at a time3 The pipe symbol (|) is used to redirect the output of one command to the input of another command. The redirection symbol (>) is used to redirect the output of a command to a file.
The command given in option C performs the following steps:
It uses the more command to display the contents of the webserver.log file.
It pipes the output of the more command to the grep command, which searches for lines that contain '*.xls', which is a pattern that matches any file name ending with .xls (a spreadsheet file extension).
It pipes the output of the grep command to the egrep command, which searches for lines that contain 'return=200', which is a pattern that matches any HTTP status code of 200 (which indicates a successful request).
It redirects the output of the egrep command to a file named accessreport.txt, which contains the date, time, and IP address associated with any spreadsheet downloads.