ExtraTopLevelOperators.fprintfn<'T> Function (F#)
The fprintfn prints to a file using the given format, and add a newline.
Namespace/Module Path: Microsoft.FSharp.Core.ExtraTopLevelOperators
Assembly: FSharp.Core (in FSharp.Core.dll)
// Signature:
fprintfn : TextWriter -> TextWriterFormat<'T> -> 'T
// Usage:
fprintfn textWriter format
Parameters
textWriter
Type: TextWriterformat
Type: TextWriterFormat<'T>
Remarks
This function is named PrintFormatLineToTextWriter in compiled assemblies. If you are accessing the function from a language other than F#, or through reflection, use this name.
Example
The following example demonstrates the use of fprintfn to print a listing of the contents of a directory to a specified file, directorylisting.txt.
let fileName = "directoryListing.txt"
let printDirectoryInfo (dirName:string) (fileName:string) =
use file = System.IO.File.CreateText(fileName)
System.IO.Directory.EnumerateFileSystemEntries(dirName)
|> Seq.iter (fun elem -> fprintfn file "%s" elem )
printDirectoryInfo @"C:\" fileName
printfn "%s" (System.IO.File.OpenText(fileName).ReadToEnd())
The following example is similar to the previous except that it also demonstrates the use of specifiers to customize the output in the format string. For more information on format specifiers, see Printf Module.
let fileName = "directoryListingXY.txt"
let printDirectoryInfo (dirName:string) (fileName:string) =
use file = System.IO.File.CreateText(fileName)
System.IO.Directory.EnumerateDirectories(dirName)
|> Seq.map (fun elem -> new System.IO.DirectoryInfo(elem))
|> Seq.iter (fun elem -> fprintfn file "%50s %A" elem.FullName elem.LastAccessTime )
System.IO.Directory.EnumerateFiles(dirName)
|> Seq.map (fun elem -> new System.IO.FileInfo(elem))
|> Seq.iter (fun elem -> fprintfn file "%50s %A" elem.FullName elem.LastAccessTime )
printDirectoryInfo @"C:\" fileName
printfn "%s" (System.IO.File.OpenText(fileName).ReadToEnd())
Platforms
Windows 8, Windows 7, Windows Server 2012, Windows Server 2008 R2
Version Information
F# Core Library Versions
Supported in: 2.0, 4.0, Portable