What exactly does this statement mean?
TextWriter textWriter = new StreamWriter(@System.Environment.GetEnvironmentVariable("OUTPUT_PATH"), true);
I have learned dotnet but haven't worked in any of the development project. Now that I am looking for a job switch, I am making use of some of the sites like Hackerrank. So I just want to know what exactly this statement do and if we omit this sentence what will happen to the code.
glad you are curious and ambitions about probramming.
The following statement
TextWriter textWriter = new StreamWriter(@System.Environment.GetEnvironmentVariable("OUTPUT_PATH"), true);
Simply creates an IO stream that allows you to write to a file on a file system. It is getting the file path that it will be writing to from the environment variable "OUTPUT_PATH" which would need to be setup external from this code.
Presumably the following lines of code will be logging some information to the file.
If you simply omit this line and there were following lines using the local variable textWriter your application would not compile. If you removed all references to this variable nothing would be written to a file.
You should be aware that using a Streamwriter can leave a file open and in use on the file system if you don't dispose of it properly. I would suggest whenever writing to a file to enclose this line in a using statement which will automatically close the file and flush whatever is in the buffer out to the file. Another thing to note is that when writing to files the streamwriter will not automatically "flush" the buffer out to file. This is particularly interesting when you are monitoring an application from files.
For more information on using a testwriter have a look at the MS docs here: https://learn.microsoft.com/en-us/dotnet/api/system.io.streamwriter?view=netcore-3.1