What does the | and grep commands do?

Question

what does the | and grep command do?

Answer

|

Is commonly called a pipe, and like the name sets it creates a way for data from the command written before it to be passed down to the command written after it, for example:

ls -l /etc | less

the first set of commands return a verbose (long) list of files and directories from the /etc directory which is where configuration files and directories are located, then the pipe passes that list to the less command which allows us to see the list in a more readable format.

grep

This command stands for global regular expression print, the value passed to it is an expression, and a second value will be a file, it will use the expression to compare it with the content inside the file, anything that contains a match will be returned to the console for us to see, for example, in the exercise the command
env | grep PATH
gets all the environment variables in our session and checks what matches the word PATH, returning all matches.

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| is used for interprocess communication between two processes.
grep is a program which helps to find certain expressions based on a pattern.

So, to give something as input to grep we use |

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