What is the purpose of the 'grep' command?

The 'grep' command is utilized primarily to search for specific patterns within text. It is a powerful and widely used command in Unix/Linux environments that allows users to identify lines in files that match a given regular expression or set of characters. Grep stands for "global regular expression print," and it effectively filters through text input or files to find occurrences of the desired strings or patterns. This capability makes it an essential tool for text processing, log file analysis, and scripting.

The other options do not align with the functionality of 'grep.' The command does not serve to list files and directories, modify content of files, or display disk space usage, each of which is handled by other specific commands in the Unix/Linux ecosystem. For example, listing files is done with commands like 'ls,' modifying files can be achieved with 'sed' or 'awk,' and checking disk space can be done using 'df.' Each command has its unique purpose, making 'grep' stand out for its specific role in pattern searching.