To use the grep command to search for a pattern in compressed .gz files at a shell prompt on a Unix or Linux system, you can use the zgrep command, which is a version of grep that is specifically designed to search compressed files.
Here is the basic syntax for using the zgrep command to search for a pattern in a compressed .gz file:
zgrep pattern file.gz
The pattern argument is a regular expression that specifies the text to search for. The file.gz argument is the name of the compressed .gz file to search.
For example, to search for the string "hello" in the compressed file file.gz, you can use the following command:
zgrep hello file.gz
This will search for the string "hello" in file.gz and display the lines that contain the string.
You can use other options and arguments to customize the search, such as the -i option to ignore case, or the -n option to display the line numbers of the matching lines.
You can also use the -r option to search recursively in a directory and its subdirectories.
For example:
zgrep -r hello directory
This will search for the string "hello" in all .gz files in the directory and its subdirectories, and display the lines that contain the string.