How to include header files in GCC search path?

Question

I have the following code in a sample file:

#include "SkCanvas.h"
#include "SkDevice.h"
#include "SkGLCanvas.h"
#include "SkGraphics.h"
#include "SkImageEncoder.h"
#include "SkPaint.h"
#include "SkPicture.h"
#include "SkStream.h"
#include "SkWindow.h"

However, this code is located in various folders within /home/me/development/skia (which includes core/ animator/ images/ ports/ svg/ and a lot more.)

How can I make GCC recognize this path?

Very useful g++ build instructions for googletest/gtest: ethz-adrl.github.io/ct/ct_core/doc/html/… — Gabriel Staples
– Gabriel Staples, Commented Apr 26, 2022 at 4:24

Alberto Chiusole · Accepted Answer · 2020-11-20 10:10:09Z

112

Try gcc -c -I/home/me/development/skia sample.c.

edited Nov 20, 2020 at 10:10

Alberto Chiusole

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answered Jun 10, 2009 at 0:25

Tim Gilbert

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6 Comments

Nav Over a year ago

Glad to see this answer here. Another point worth mentioning would be that when you have many ".c" source files, it's necessary to specify each and every one of them in the commandline itself. You can't just do something like a -I to specify that all source files are in a certain directory.

CodyBugstein Over a year ago

If the header is in the same directory as the source, do you need a special include? I can't get my code to compile either way, and I'm not sure what the problem is

Robert Schwarz Over a year ago

According to this answer to a similar question, gcc would not search the subdirectories for the different header files automatically. Instead, pkg-config could produce the proper -I option?

falsePockets Over a year ago

What's the difference between -I and -L?

Aviv Cohn Over a year ago

@EdwinPratt Perhaps you meant to say that -L tells GCC where to look for binary libraries to include (which are specified with -l). And -I tells GCC where to look for header files to include.

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paxdiablo · Accepted Answer · 2009-06-10 01:04:23Z

41

The -I directive does the job:

gcc -Icore -Ianimator -Iimages -Ianother_dir -Iyet_another_dir my_file.c

edited Jun 10, 2009 at 1:04

paxdiablo

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answered Jun 10, 2009 at 0:21

Reginaldo

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1 Comment

Gabriel Staples Over a year ago

To anyone needing this: it looks like you can include directories with spaces in them with quotes: -I"some path/with spaces".

Scott P. · Accepted Answer · 2020-09-23 14:36:56Z

Using environment variable is sometimes more convenient when you do not control the build scripts / process.

For C includes use C_INCLUDE_PATH.

For C++ includes use CPLUS_INCLUDE_PATH.

See this link for other gcc environment variables.

Example usage in MacOS / Linux

# `pip install` will automatically run `gcc` using parameters
# specified in the `asyncpg` package (that I do not control)

C_INCLUDE_PATH=/home/scott/.pyenv/versions/3.7.9/include/python3.7m pip install asyncpg

Example usage in Windows

set C_INCLUDE_PATH="C:\Users\Scott\.pyenv\versions\3.7.9\include\python3.7m"

pip install asyncpg

# clear the environment variable so it doesn't affect other builds
set C_INCLUDE_PATH=

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