Final answer:
The command to search the contents of a file for a particular pattern is 'grep', a utility for searching text using regular expressions.
Step-by-step explanation:
The command that allows a user to search the contents of a file for a particular pattern is grep.
grep, which stands for "global regular expression print," is a powerful utility available on Unix and Unix-like operating systems. It is used to search for text patterns, specified as regular expressions, within files. For example, if you wanted to find the word "example" in a file named "sample.txt", you would use the command grep 'example' sample.txt. This command will search through the file and output every line that contains the pattern "example".
In contrast, the touch command is used to create empty files or update the timestamps on existing files, and the find command is used to search for files and directories within a file system, but not to search within the contents of the files themselves.