opens a file to write output to it, and returns an OutputStream object.


opens a new file in the default area for temporary files on your computer system.

Details and Options

  • OpenWrite deletes any existing contents in a file, and prepares to write output starting at the beginning of the file.
  • The following options can be given:
  • BinaryFormatFalsewhether to use binary format for the file
    CharacterEncodingAutomaticwhat raw character encoding to use
    FormatTypeInputFormdefault format for printing expressions
    NumberMarks$NumberMarkswhen to use ` marks in approximate numbers
    PageWidth78number of character widths per line
    TotalWidthInfinitymaximum number of character widths for a single expression
    MethodAutomaticstream method to use
  • On computer systems that support pipes, OpenWrite["!command"] runs the external program specified by command, and opens a pipe to send input to it.
  • If OpenWrite does not succeed in opening a particular file or pipe, it generates a message and returns $Failed.
  • OpenWrite resolves file names according to the procedure described in "Files and Streams".
  • OpenWrite returns OutputStream["name",n], where name is the full name of a file or command, and n is a serial number that is unique across all streams opened in the current Wolfram System session.
  • SetOptions can be used to change the properties of an output stream after it is already open.
  • Functions like Put and Write automatically open the files or pipes they need, if they are not already open.
  • With the default setting BinaryFormat->False, the setting for CharacterEncoding is taken to be "ASCII".
  • OpenWrite[] always creates a new file that does not already exist, in the directory given by $TemporaryDirectory.
  • With the Method option, the stream is opened using the given input stream method. This overrides the default way that OpenWrite resolves file names.
  • OpenWrite[File["file"]] is also supported.


open allclose all

Basic Examples  (1)

Create and open a new stream for writing:

Write an expression to the stream:

Close the stream:

Print the resulting file:

Scope  (1)

Write an expression to the file specified by the File object:

Wolfram Research (1988), OpenWrite, Wolfram Language function, (updated 2016).


Wolfram Research (1988), OpenWrite, Wolfram Language function, (updated 2016).


Wolfram Language. 1988. "OpenWrite." Wolfram Language & System Documentation Center. Wolfram Research. Last Modified 2016.


Wolfram Language. (1988). OpenWrite. Wolfram Language & System Documentation Center. Retrieved from


@misc{reference.wolfram_2024_openwrite, author="Wolfram Research", title="{OpenWrite}", year="2016", howpublished="\url{}", note=[Accessed: 20-July-2024 ]}


@online{reference.wolfram_2024_openwrite, organization={Wolfram Research}, title={OpenWrite}, year={2016}, url={}, note=[Accessed: 20-July-2024 ]}