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The shell splits tokens based on the contents of the IFS environment variable. Its default value is \t\n; i.e., whitespace, tab, and newline. Expanding "$@" gives you a pristine copy of the arguments passed. Expanding $@ may not.
The shell treats several parameters specially. These parameters may only be referenced; assignment to them is not allowed. [...]? Expands to the exit status of the most recently executed foreground pipeline. ANSI C and POSIX then recommend that: 0 means the program was successful. other values: the program failed somehow.
The above (along with many more forms of ${parameter…something_else} constructs) are discussed at greater length in the shell’s man page, bash(1). A Note on Quotes. Note that you should always quote shell variables unless you have a good reason not to, and you’re sure you know what you’re doing. By contrast, while braces can be ...
What is the difference between =, == and -eq in shell scripting? Is there any difference between the following?
Shell - "Shell" is a program, which facilitates the interaction between the user and the operating system (kernel). There are many shell implementations available, like sh, Bash, C shell, Z shell, etc. Using any of the shell programs, we will be able to execute commands that are supported by that shell program. Bash - It derived from Bourne ...
In shell, when you see $ command one && command two the intent is to execute the command that follows the && only if the first command is successful. This is idiomatic of Posix shells, and not only found in Bash. It intends to prevent the running of the second process if the first fails.
IMHO best way is you could simply do man test for all these details. It is very well explained there. As follows is the text from man page.
Kernel Version. If you want kernel version information, use uname(1). For example: $ uname -a Linux localhost 3.11.0-3-generic #8-Ubuntu SMP Fri Aug 23 16:49:15 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux
In man bash we can read in Shell Builtin Commands section : Unless otherwise noted, each builtin command documented in this section as accepting options preceded by -accepts --to signify the end of the options. The :, true, false, and test builtins do not accept options and do not treat --specially.
You can find a very nice reference for bash's [aka test builtin's operators here, or by running help test in a bash shell or info bash test or info bash '[' from any shell¹. If you are using a different shell, just search for the description of its [ or test builtin in its documentation of if it doesn't have such a builtin², in the man page ...