apparently Richard Stallman was one of the major contributors to cat ; you can use it to open a file and output it to something else.I used it in a slackbuild like so:
cat $CWD/slack-desc > $PKG/install/slack-desc
Even though I know i don't need to use 'cat file | grep something', i still do it every day from muscle memory haha.. could be i'm catting something, then just uparrow and add the grep to the end most of the time though.
Hey there @daysaputra - welcome to the forum. You're in the right place.. there are some tutorials here and plenty of other articles and things to read. I wrote a little ebook (in my signature) that might help, but mainly try to use Linux as much as you can and things will start seeping in.
hey @daysaputra this ism y philosophy- you can read as much fishing books as you like; you then have "head knowledge" . the way to get actual knowledge is just to do some actual fishing. Thus google for some linux command lines and just try them. One question do you have the means of trying linux command line ? Do you have access to any linux OS or Windows Subset for Linux (Windows 10). if not thats your first objective.
After that its just a case of opening a terminal window and stating with basics.