How can I add a default include path for GCC in Linux?

Question

I'd like GCC to include files from $HOME/include in addition to the usual include directories, but there doesn't seem to be an analogue to $LD_LIBRARY_PATH.

I know I can just add the include directory at command line when compiling (or in the makefile), but I'd really like a universal approach here, as in the library case.

Here is link to GCC 4.8.1 manual where C_INCLUDE_PATH and CPLUS_INCLUDE_PATH environment variables are documented. — mloskot
– mloskot, Commented Jan 23, 2010 at 16:59

Will Chen · Accepted Answer · 2022-12-14 18:05:16Z

501

Try setting C_INCLUDE_PATH (for C header files) or CPLUS_INCLUDE_PATH (for C++ header files) environment variables.

As Ciro mentioned, CPATH will set the path for both C and C++ (and any other language).

On Windows these may be set to semicolon-separated lists. On most other platforms they may be set to colon-separated lists.

More details in GCC's documentation.

edited Dec 14, 2022 at 18:05

Will Chen

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answered Feb 17, 2009 at 21:31

jcrossley3

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2 Comments

Peter Mortensen Over a year ago

What is this "CPATH" line that was added 2016? It seems to be completely bogus. Is it? At best, it could refer to a comment that has now been deleted. By user "Ciro Santilli"? Does "CPATH" actually mean "C_INCLUDE_PATH"? Or is it literally "CPATH"? Perhaps elaborate in the answer with an explanation and/or a direct reference to documentation?

Will Chen Over a year ago

@PeterMortensen CPATH in the GCC/CPP docs. Edit suggested, awaiting approval.

agilgur5 · Accepted Answer · 2025-10-18 03:08:01Z

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Create an alias for gcc with your favorite includes:

alias mygcc='gcc -I/whatever/'

edited Oct 18 at 3:08

agilgur5

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answered Feb 17, 2009 at 21:31

dirkgently

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7 Comments

Iulius Curt Over a year ago

I think there should be no space after -I

h4unt3r Over a year ago

just a matter of habit to omit the space, just like you'd type -l<libnam> to link Just note that creating an alias is a very poor solution, really you would build a list of your 'favorite includes' and add them in your makefile.

Jori Over a year ago

"The second alternative with the library as a separate argument is only for POSIX compliance and is not recommended.", according to the GCC manual.

einpoklum Over a year ago

Not a good idea. This is non-composable (what if you want another dir? what if you want some other GCC switch) and may confuse various scripts or automated tools which make assumptions about gcc.

crow Over a year ago

@h4unt3r why is an alias poor?

eliotttak Oct 17 at 20:13

Because, as einpoklum said, "this is non-composable (what if you want another dir? what if you want some other GCC switch) and may confuse various scripts or automated tools which make assumptions about gcc".

crow Oct 19 at 6:38

Oh, I didn't know einpoklum's was a follow up to that point. If that's the case, then sounds like a moot point. If you want more than what an alias provides, then simply don't use an alias. That doesn't make it a poor solution, just a solution to a problem other than yours.

Peter Mortensen · Accepted Answer · 2022-11-05 01:06:45Z

21

Just a note: CPLUS_INCLUDE_PATH and C_INCLUDE_PATH are not the equivalent of LD_LIBRARY_PATH.

LD_LIBRARY_PATH serves the ld (the dynamic linker at runtime) whereas the equivalent of the former two that serves your C/C++ compiler with the location of libraries is LIBRARY_PATH.

edited Nov 5, 2022 at 1:06

Peter Mortensen

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answered Dec 9, 2018 at 9:08

Dagim Sisay

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1 Comment

Peter Mortensen Over a year ago

This seems to be a response to jcrossley3's answer, not an answer. Stack Overflow is not a forum. Related: Why do I need 50 reputation to comment? What can I do instead?.

0xC0000022L · Accepted Answer · 2021-06-16 11:45:49Z

11

A gcc spec file can do the job, however all users on the machine will be affected.

See HOWTO Use the GCC specs file

edited Jun 16, 2021 at 11:45

0xC0000022L

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answered Oct 6, 2009 at 17:22

dimba

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3 Comments

Thomas Over a year ago

The link is dead. Would be great if you could update this answer with the actual info.

Gwyneth Llewelyn Over a year ago

@Thomas fortunately, it's still available on Archive.org!

Thomas Over a year ago

Better than nothing, but Always quote the most relevant part of an important link, in case the external resource is unreachable or goes permanently offline..

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