.IN File Extension

3 file types use the .in file extension.

Autoconf Input File

Developer GNU Project
4.3  |  29 Votes

What is an IN file?

An IN file is an input file referenced by GNU Autoconf when building an application. One or more .in or .h.in files may be referenced by an Autoconf script (.AC file) when the configure process is run. IN files define variables, such as an app's version number and release date, which are referenced during program installation. IN files may also be used to check for the presence or absence of features in a specific installation.

More Information

Autoconf is part of the GNU build system, which creates custom builds of applications for different platforms. It is one of several GNU build tools, which include Automake, Gnulib, and Libtool.

NOTE: While the GNU community previously encouraged developers to name their top-level configuration file configure.in, they now recommend developers name their top-level file configure.ac.

Common IN Filenames

config.h.in - a header file used to define C macros

makefile.in - a build file used to compile a program

configure.in - a source file from which Autoconf generates a configure script

How to open an IN file

You can open an IN file in a text editor, such as Notepad (Windows) or TextEdit (Mac). However, if you want to edit an IN file, it's best to use a source code editor, such as NotePad++ or Atom. These applications provide helpful source code editing tools and highlight the syntax correctly.

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Programs that open or reference IN files


Input File

Developer N/A
3.6  |  31 Votes

File used by the Consolidated Model of Fire and Smoke Transport (CFAST), a program used to model fire and smoke impact on buildings; contains input data, like room specifications, accessed by the program to model fire and smoke effects.

More Information

NOTE: IN files are generic, they can be used by other programs for data input.

Programs that open or reference IN files


Spyware File

Developer N/A
2.2  |  49 Votes

An IN file may also be a generic file used by some spyware programs to track activity on a computer. If you cannot verify an IN file's legitimacy or source, you should check it with an anti-spyware program.

More Information

Some examples of spyware files with a ".in" extension include:

  • "config.h.in"
  • "configureconfigure.in"
  • "makefile.in"
  • "net.h.in"

Programs that open or reference IN files

Should not be opened

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