Which command allows you to search for specific text strings within a file?

The command that allows you to search for specific text strings within a file is 'grep'. It stands for "Global Regular Expression Print" and is specifically designed for searching plain-text data sets for lines that match a regular expression. When you use 'grep', you can specify the text string you are looking for, and it will scan the specified files, returning any lines that contain that text. This functionality makes it a powerful tool for browsing through text files or output from other commands.

In contrast, 'search' is not a standard command in most Linux distributions, making it an invalid option for this functionality. The 'find' command is typically used to locate files and directories within the file system based on criteria such as name, type, or attributes, but it does not specifically search the contents of files for text strings. 'Locate', on the other hand, is utilized to find files quickly using a pre-built database of file names but does not search within files for specific text, which is the key requirement of the question. Thus, 'grep' is the accurate and most relevant command for searching specific text strings within files.