Can't find the 'libpq-fe.h header when trying to install pg gem

Question

I am using the Ruby on Rails 3.1 pre version. I like to use PostgreSQL, but the problem is installing the pg gem. It gives me the following error:

Answer 1

For CentOS 6.4,

yum install postgresql-devel
gem install pg

worked well!

Answer 2

On macOS (previously Mac OS X and OS X), use Homebrew to install the proper headers:

brew install postgresql

and then running

gem install pg

should work.

Alternatively, instead of installing the whole postgresql, you can brew install libpq and export the correct PATH and PKG_CONFIG_PATH as explained in the 'Caveats' section

Answer 3

A more general answer for any Debian-based distribution (which includes Ubuntu) is the following. First, install the apt-file package running as root:

apt-get install apt-file

This allows you to search for packages containing a file. Then, update its database using

apt-file update

(this can be run as normal user). Then, look for the missing header using:

apt-file search libpq-fe.h

On my machine, this gives:

libpq-dev: /usr/include/postgresql/libpq-fe.h
postgres-xc-server-dev: /usr/include/postgres-xc/server/gtm/libpq-fe.h

There you go !

Answer 4

For MacOS without installing PostgreSQL server:

brew install libpq
gem install pg -- --with-pg-config="/usr/local/Cellar/libpq/9.6.6/bin/pg_config"

Answer 5

The location of libpq-fe.h depends on where your PostgreSQL install is (which depends on how you installed it). Use locate (http://en.wikipedia.org/wiki/Locate_%28Unix%29) to find the libpq-fe.h file on your machine. If it exists, it will be in the include directory of your PostgreSQL install.

$ locate libpq-fe.h
/Library/PostgreSQL/9.1/include/libpq-fe.h

The bin directory, which contains pg_config, will be in the same directory as the include directory. As the error suggests, use the --with-pg-config option to install the gem:

$ gem install pg --with-pg-config="/Library/PostgreSQL/9.1/bin/pg_config"

Note that you may need to run updatedb if you have never used locate or if you haven't updated since installing PostgreSQL.

Answer 6

Just for the record:

Ruby on Rails 4 application in OS X with PostgresApp (in this case 0.17.1 version needed - kind of an old project):

gem install pg -v '0.17.1' -- --with-pg-config=/Applications/Postgres.app/Contents/Versions/9.3/bin/pg_config