What does this command do?

command base64 /dev/urandom | head -n 700 > NewFile.txt

Where did you find this command? What are you trying to achieve?

Well, the base64 and head are programs, so the'll have reference manuals:

The first one converts binary data to a text-encoding suitable for certain situation.
The | pipe character takes the output from the first program and sends at input to the second.
The second program, with the -n 700 option, takes the first 700 lines and then stops.

The first file, /dev/urandom, is a connection from the kernel's random number source device.
The second file, NewFile.txt, is just a regular file which will contain the above mentioned 700 lines by virtue of a shell redirection indicated by the > operator. See also chapter 6 of the book The Linux Command Line.

In short, the line you ask about will produce a file containing 700 lines of random letter, numbers, and a few symbols.

Two threads started so far with questions which look like homework.

One more thing to mention:
when the second command terminates then it closes the pipe.
Then the first command gets a SIGPIPE that tells it to terminate.

1 members found this post helpful.

Thank you everyone for all your help. all done now.