What mean file with extension "h.in"?

Question

I am studying the C language, and I saw a new extension that I had not seen before.

What do files with the extension like library.h.in mean?

Is it as the simple header with extension ".h"? What's the difference?

Hmm weird [this](http://www.fileinfo.com/extension/in) link says they might be spyware? — Mike Christensen, Jan 10 '13 at 00:26
@MikeChristensen I'm more suspicious of that page than of a normal `Makefile.in` or `config.h.in`. — Daniel Fischer, Jan 10 '13 at 00:28
@DanielFischer - Yea, they might just be trying to sell you virus scanners.. — Mike Christensen, Jan 10 '13 at 00:30

score 47 · Accepted Answer · answered Jan 10 '13 at 00:30

These files are usually the input for autoconf which will generate final .h files.

Here's an example from PCRE:

#define PCRE_MAJOR          @PCRE_MAJOR@
#define PCRE_MINOR          @PCRE_MINOR@
#define PCRE_PRERELEASE     @PCRE_PRERELEASE@
#define PCRE_DATE           @PCRE_DATE@

Autoconf will replace all variables (@…@) with the respective values and the result will be a .h file.

score 22 · Answer 2 · edited Oct 28 '15 at 14:38

22

Typically, a .h.in file is a header template that is filled in to become the actual header by a configure script based on the outcome of several tests for features present on the target platform.

edited Oct 28 '15 at 14:38

Jeff Camera

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answered Jan 10 '13 at 00:24

Daniel Fischer

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This file extension is also popular among other build tools, e.g.`cmake` – szx Jan 10 '13 at 00:35

syb0rg · Answer 3 · 2016-01-12T21:48:16.450

6

Files ending with .in are typically template files used by a program called configure that generates a new file without the extension after substituting for variable expansions. I.e., if you're looking at a source tree that has files called, e.g. Makefile.in in the tree, then ./configure will generate a usable Makefile that can be used to "make" from source.

edited Jan 12 '16 at 21:48

answered Jan 10 '13 at 00:25

syb0rg

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What mean file with extension "h.in"?

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