Additive color mixing begins with black and ends with white; as more color is added, the result is lighter and tends to white. The RGB colors are light primaries and colors are created with light. Percentages of red, green, & blue light are used to generate color on a computer screen.
In shell scripting we often need to check if file or directory exists and take appropriate action. This post show you how to check it and how this check use in your script. For checking we will use file test operators -f for file and -d for directory, which return TRUE if file or directory exists. And here is output of the script.
In a bash script, anything following a pound sign # (besides the shell name on the first line) is treated as a comment. ie the shell ignores it. It is there for the benifit of people reading the script. $USER and $PWD are variables. These are standard variables defined by the bash shell itself, they needn't be defined in the script. Note that the variables are expanded when the variable name is inside double quotes.