less: You might be familiar with ‘cat’. ‘less’ is a much better way to inspect large files on the command line. You’ll get a screen-full of text at a time, but no more. You can move a line or window up or down. You can search for a pattern by typing /pattern. When you’re done, hit q to exit the less viewer.

touch: ‘touch’ is basically for changing file access and modification times. But it’s a bonus that if the file doesn’t exist, it will create it.

history, !!, and !$: ‘history’ shows a numbered list of many of your recent commands on console. Then, to execute one of them, just type an exclamation mark and the history number. It’s even quicker to access the last command and last argument you used. For the latest command, use !!; the usual use case given for this is adding sudo to the front of a command. For the latest argument, use !$;

yes: ‘yes’ outputs argument forever. By default, it prints ‘y’ forever.

cal: Displays a very nice calendar with current date highlighted.

seq: This command prints sequences of numbers. User can define start number, interval, end number and many other options.

bc: A very precise calculator. Really useful for performing calculations on large numbers.

factor: A very good mathematical utility for finding prime integer factors.

stat: display file or file system status

tac: reverse of 'cat', print a file line by line in reverse order.

ldd: prints shared library information. In OS X, we use otool for the same purpose.

iostat: CPU and disk usage stats

lsof: List Open Files

netstat: show network status

PS: I've not given examples but linked to man pages on purpose, so that readers can learn by experiment.


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