BSD syntax of commands

We use ps aux to display the processes of all users. But, we notice here that we don't use the - sign with options that we were using till now. So, using options without - is known as BSD syntax to write commands. The other one (one with -), which we use regularly, is known as Standard syntax to write commands.

ps command has been in use since the early versions of Unix. When it was written, BSD syntax was in use to write commands. So, when standard syntax came into the scene, we started to use - with options. But people who used BSD syntax didn't like that they had to modify their programs and habits due to the new syntax.

So, the commands were re-defined with the standard syntax without removing their compatibility with the BSD syntax. So, the commands which are very old (which were written when BSD syntax was in use) like ps command supports both BSD syntax and standard syntax.

Note that ps -aux is distinct from ps aux. Feel free to use man ps to know more about it.

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BSD syntax of commands

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