1. What do the square brackets [ ] mean in an ubuntu terminal command's synopsis?
May be you have seen the various symbols in the manual pages of the command while accessing the man page, like this [ ] which is called as square brackets. Please look into the square bracket first :
[ ] square bracket is nothing just an optionally, Things inside the square brackets are optional.
[-a] option above means that the while writing the which command, there is no compulsion to pass argument that is -a. Means [-a] is optional as the -a is written in square bracket
Alternatively, you can use the following command (without using -a, as it is optional)
This is how the use of square brackets [ ] in Ubuntu can be considered as, But careful the next command with the square brackets is going to be something surprising,
square brackets containing pipe-separated items [ … | … ] mean that you must specify one of those items. for example for the below mentioned command you are supposed to use either of the both argument a or f , you must specify one of the both, but not both like -af
2. What do the angular brackets < > mean in an ubuntu terminal command's synopsis?
You may have come across while using the ubuntu systems and the various symbols like this < > which is called as angular brackets, which is nothing just a mandatory symbol. Anything inside the angular bracket < > is mandatory
<FILENAME> is mandatory to execute the command. In order to execute the which command, it is mandatory to pass the filename.
To sum up, Anything inside square brackets [ ] is optional and anything inside the < > bracket is mandatory That’s all folks for the day !! , Happy Ubuntu days Ahead !