Source Line, File, and Path Identifiers

The identifiers __LINE__, __SOURCE_DIRECTORY__ and __SOURCE_FILE__ are built-in values that enable you to access the source line number, directory and file name in your code.




Each of these values has type string.

The following table summarizes the source line, file, and path identifiers that are available in F#. These identifiers are not preprocessor macros; they are built-in values that are recognized by the compiler.

Predefined identifier Description
__LINE__ Evaluates to the current line number, considering #line directives.
__SOURCE_DIRECTORY__ Evaluates to the current full path of the source directory, considering #line directives.
__SOURCE_FILE__ Evaluates to the current source file name, without its path, considering #line directives.

For more information about the #line directive, see Compiler Directives.


The following code example demonstrates the use of these values.

let printSourceLocation() =
    printfn "Line: %s" __LINE__
    printfn "Source Directory: %s" __SOURCE_DIRECTORY__
    printfn "Source File: %s" __SOURCE_FILE__


Line: 4
Source Directory: C:\Users\username\Documents\Visual Studio 2017\Projects\SourceInfo\SourceInfo
Source File: Program.fs

See also