Posted by OmegaKV on
URL: https://mikraite.arkian.net/My-Bash-Tutorial-tp4442p4492.html

A command's output can be filtered by grep if it is piped to grep.

For example:

"ps aux | grep firefox" to look for instances of firefox running. I'm not sure if "ps aux" works on mac, but it prints a table containing the names of all the running processes and their process IDs, username, etc.

At work we have a command that monitors a certain reading and prints a bunch of usually unnecessary diagnostic info. The command runs indefinitely. Every time the reading value changes, it prints the value (e.g. "value: 5.4") plus all the diagnostic info all over again. The diagnostic info is a distraction that makes it difficult to see how the reading value is changing. So I can do 'monitor | grep "value:"', so that when the reading value changes it prints only the one line containing the value, and this makes it easier for a human to see how the value is changing.

If the reading value still changes too rapidly for me to follow what is happening, I might want to be able to control when it prints each output line. To do this I modify the command to the following: 'monitor | grep "value:" | more', and now it only prints each new output line when I press enter.