I'm trying to learn regular expressions, and so I created a file with some characters in it. When I use the cat command and pipe it to rgrep command with an argument to filter out text, the resulting output is "filename:filtered_text".
cat regex.txt | rgrep -E '^a' regex.txt:a regex.txt:aa regex.txt:aaa regex.txt:aaaa regex.txt:aaaaa regex.txt:aaaaaa file:acpi file:adduser.conf file:aliases file:aliases.db file:alternatives file:anacrontab file:apache2 file:apg.conf file:apm file:apparmor file:apparmor.d file:apport file:appstream.conf file:apt file:avahi
Not only that it also checks for other files in the folder and if they match the regular expression it shows them as well, even though I only piped a single file.
How do I get a normal output with only the contents of the file I've passed into cat?