Which command is used to search for a string within files in Linux?

The command that is used to search for a string within files in Linux is 'grep'. This command is specifically designed to search through text data and is one of the most powerful tools available for text processing in Linux. When you run 'grep' followed by the pattern you're searching for and the file (or files) you want to search within, it will output lines from those files that contain the specified string or pattern.

For instance, using a command like grep "hello" file.txt will return all lines in "file.txt" that contain the word "hello". 'grep' supports regular expressions, making it particularly versatile for complex pattern matching.

Other commands like 'find' and 'locate' serve different purposes. 'find' is used to search for files and directories based on various criteria such as name, size, or modification time, rather than searching within the contents of files. Similarly, 'locate' quickly finds files by searching a prebuilt database of file paths, but it does not inspect the contents of those files. The term 'search' is not a specific command in Linux; it may refer to the action of searching but does not represent a valid command on its own as recognized in the Linux command line.