unable to install pg gem

Question

I tried using gem install pg but it doesn't seem to work.

gem install pg gives this error

Temporarily enhancing PATH to include DevKit...
Building native extensions.  This could take a while...
ERROR:  Error installing pg:
        ERROR: Failed to build gem native extension.

C:/Ruby/bin/ruby.exe extconf.rb
checking for pg_config... no
No pg_config... trying anyway. If building fails, please try again with
 --with-pg-config=/path/to/pg_config
checking for libpq-fe.h... no
Can't find the 'libpq-fe.h header
*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of
necessary libraries and/or headers.  Check the mkmf.log file for more
details.  You may need configuration options.

Provided configuration options:
        --with-opt-dir
        --without-opt-dir
        --with-opt-include
        --without-opt-include=${opt-dir}/include
        --with-opt-lib
        --without-opt-lib=${opt-dir}/lib
        --with-make-prog
        --without-make-prog
        --srcdir=.
        --curdir
        --ruby=C:/Ruby/bin/ruby
        --with-pg
        --without-pg
        --with-pg-dir
        --without-pg-dir
        --with-pg-include
        --without-pg-include=${pg-dir}/include
        --with-pg-lib
        --without-pg-lib=${pg-dir}/lib
        --with-pg-config
        --without-pg-config
        --with-pg_config
        --without-pg_config


Gem files will remain installed in C:/Ruby/lib/ruby/gems/1.8/gems/pg-0.10.1 for
inspection.
Results logged to C:/Ruby/lib/ruby/gems/1.8/gems/pg-0.10.1/ext/gem_make.out

Answer 1

I hadn't postgresql installed, so I just installed it using

sudo apt-get install postgresql postgresql-server-dev-9.1

on Ubuntu 12.04.

This solved it.

---

Update:

Use the latest version:

sudo apt-get install postgresql-9.3 postgresql-server-dev-9.3

Answer 2

I had to do this on CentOS 5.8. Running bundle install kept causing issues since I couldn't force it to use a particular PG version.

I can't yum erase postgresql postgresql-devel either, because of dependency issues (it would remove php, http etc)

The solution? Mess $PATH temporarily to give preference to the update pgsql instead of the default one:

export PATH=/usr/pgsql-9.2/bin:$PATH
bundle install

Basically, with the above commands, it will look at /usr/pgsql-9.2/bin/pg_config before the one in /usr/bin/pg_config