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WriteLine["file","string"]

writes "string" to a file, followed by a newline.

WriteLine[stream,"string"]

writes "string", followed by a newline, to the specified output stream.

WriteLine[proc,"string"]

writes "string" to an external process proc.

Details
Details and Options Details and Options
Examples  
Basic Examples  
Scope  
Properties & Relations  
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WriteLine

WriteLine["file","string"]

writes "string" to a file, followed by a newline.

WriteLine[stream,"string"]

writes "string", followed by a newline, to the specified output stream.

WriteLine[proc,"string"]

writes "string" to an external process proc.

Details

  • WriteLine will open a file for writing, erasing all existing data, if it is not already open.
  • WriteLine[File["file"],…] is also supported.

Examples

open all close all

Basic Examples  (2)

Write a string to a temporary file:

Wolfram Language code: file = CreateFile[];
Wolfram Language code: WriteLine[file, "hello world"]

Print the file:

Wolfram Language code: FilePrint[file]

Delete the temporary file:

Wolfram Language code: DeleteFile[file]

Start the system shell process:

Wolfram Language code: process = StartProcess[$SystemShell]

Write a command into the shell process:

Wolfram Language code: WriteLine[process, "echo example line"];

Read one line from the shell output:

Wolfram Language code: ReadLine[process]

Scope  (2)

Open a stream:

Wolfram Language code: str = OpenWrite[];

Write a line into the file:

Wolfram Language code: WriteLine[str, "1234"];

Close the stream:

Wolfram Language code: Close[str];

Print the contents that were written:

Wolfram Language code: FilePrint[First[str]]

Create a temporary file:

Wolfram Language code: file = File[CreateFile[]]

Write a line of text:

Wolfram Language code: WriteLine[file, "this is some text"]
Wolfram Language code: WriteLine[file, "this is more text"]
Wolfram Language code: Close[file]

Both lines were written:

Wolfram Language code: FilePrint[file]

Delete the temporary file:

Wolfram Language code: DeleteFile[file]

Properties & Relations  (1)

WriteLine inserts line breaks after each string it writes:

Wolfram Language code: file = File[CreateFile[]]
Wolfram Language code: WriteLine[file, "this is some text"]; WriteLine[file, "this is more text"]; Close[file]
Wolfram Language code: FilePrint[file]

WriteString does not insert line breaks automatically:

Wolfram Language code: WriteString[file, "this is some text"]; WriteString[file, "this is more text"]; Close[file]
Wolfram Language code: FilePrint[file]

Delete the temporary file:

Wolfram Language code: DeleteFile[file]
Wolfram Research (2014), WriteLine, Wolfram Language function, https://reference.wolfram.com/language/ref/WriteLine.html (updated 2016).

Text

Wolfram Research (2014), WriteLine, Wolfram Language function, https://reference.wolfram.com/language/ref/WriteLine.html (updated 2016).

CMS

Wolfram Language. 2014. "WriteLine." Wolfram Language & System Documentation Center. Wolfram Research. Last Modified 2016. https://reference.wolfram.com/language/ref/WriteLine.html.

APA

Wolfram Language. (2014). WriteLine. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/WriteLine.html

BibTeX

@misc{reference.wolfram_2026_writeline, author="Wolfram Research", title="{WriteLine}", year="2016", howpublished="\url{https://reference.wolfram.com/language/ref/WriteLine.html}", note=[Accessed: 13-June-2026]}

BibLaTeX

@online{reference.wolfram_2026_writeline, organization={Wolfram Research}, title={WriteLine}, year={2016}, url={https://reference.wolfram.com/language/ref/WriteLine.html}, note=[Accessed: 13-June-2026]}