Can't find the PostgreSQL client library (libpq)

Question

I'm trying to install PostgreSQL for Rails on Mac OS X 10.6. First I tried the MacPorts install but that didn't go well so I did the one-click DMG install. That seemed to work.

I suspect I need to install the PostgreSQL development packages but I have no idea how to do that on OS X.

Here's what I get when I try to do sudo gem install pg:

$ sudo gem install pg
Building native extensions.  This could take a while...
ERROR:  Error installing pg:
    ERROR: Failed to build gem native extension.

        /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/bin/ruby extconf.rb
checking for pg_config... yes
Using config values from /Library/PostgreSQL/8.3/bin/pg_config
checking for libpq-fe.h... yes
checking for libpq/libpq-fs.h... yes
checking for PQconnectdb() in -lpq... no
checking for PQconnectdb() in -llibpq... no
checking for PQconnectdb() in -lms/libpq... no
Can't find the PostgreSQL client library (libpq)
*** 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=/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/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
    --with-pqlib
    --without-pqlib
    --with-libpqlib
    --without-libpqlib
    --with-ms/libpqlib
    --without-ms/libpqlib


Gem files will remain installed in /Library/Ruby/Gems/1.8/gems/pg-0.11.0 for inspection.
Results logged to /Library/Ruby/Gems/1.8/gems/pg-0.11.0/ext/gem_make.out

Answer 1

The error message is right there:

Can't find the PostgreSQL client library (libpq)

Solution 1: Postgres.app

If you are using the Postgres.app make sure to have add its lib and bin directories to your path:

export PATH="/Applications/Postgres.app/Contents/Versions/latest/bin:$PATH"
export PATH="/Applications/Postgres.app/Contents/Versions/latest/lib:$PATH"
gem install pg

You might want to add these directories to your PATH in your ~/.zshrc as well.

Solution 2: homebrew

If you have installed postgres from homebrew, you can fix that error by using homebrew to install libpq

brew install libpq

The following, or a similar, message will appear:

If you need to have libpq first in your PATH, run:
  echo 'export PATH="/opt/homebrew/opt/libpq/bin:$PATH"' >> ~/.zshrc

For compilers to find libpq you may need to set:
  export LDFLAGS="-L/opt/homebrew/opt/libpq/lib"
  export CPPFLAGS="-I/opt/homebrew/opt/libpq/include"

You can then install the pg gem:

export PATH="/opt/homebrew/opt/libpq/bin:$PATH"
gem install pg

Answer 2

Most of those answers focus on giving you one command that just works. However they only work for some particular scenarii. If you have trouble figuring out which command you should run, you better understand what is happening.

Why doesn't it work?

The pg gem is a native extension written in C. It relies on the libpq library which is the PostgreSQL library for C applications.

So, during its build, the pg gem needs to be able to find the library libqp compiled for the same architecture (for example x86_64 or arm64).

There can be a mismatch if:

• you are on a m1 macbook (apple silicon) but have installed postgres in rosetta 2 mode.
• you are on a 64-bit computer but have installed postgres in 32-bit mode.

If you end up in this situation, you have several options:

• try to compile the pg gem in the same architecture as postgres
• reinstall postgres to match the architecture in which the pg gem is built (by default it's the same as ruby's)

Example

For instance, in my case, I have a m1 macbook. I have installed ruby in "rosetta 2" mode (x86_64) and postgres in "native" mode (arm64).

You can check the architecture with the lipo -info command:

which ruby
# You might need to use a different command if you use a ruby version manager
# "which ruby" if you use rvm
# "rbenv which ruby" if you use rbenv
# "asdf which ruby" if you use asdf
=> /Users/leo/.rbenv/versions/2.6.6/bin/ruby

lipo -info /Users/leo/.rbenv/versions/2.6.6/bin/ruby
=> /Users/leo/.rbenv/versions/2.6.6/bin/ruby is architecture: x86_64

which postgres
=> /opt/homebrew/bin/pg_config

lipo -info /opt/homebrew/bin/pg_config
=> Non-fat file: /opt/homebrew/bin/pg_config is architecture: arm64

To solve this, in my case, I just had to add to the PATH another version of postgres compiled in x86_64. It allowed the pg gem to be able to find binaries in the right architecture:

export PATH=/usr/local/Cellar/postgresql/13.2_1/bin:$PATH
gem install pg

# and finally 🎉
=> Building native extensions. This could take a while...
=> Successfully installed pg-1.2.3
=> Parsing documentation for pg-1.2.3
=> Installing ri documentation for pg-1.2.3
=> Done installing documentation for pg after 1 seconds
=> 1 gem installed

Answer 3

If you are getting this error in Mac M1 pro, Silicon chip

Issue:

checking for PQconnectdb() in -lpq... no
checking for PQconnectdb() in -llibpq... no
checking for PQconnectdb() in -lms/libpq... no
Can't find the PostgreSQL client library (libpq)

Solution:

Install libpq via homebrew and add it to the PATH

brew install libpq
echo 'export PATH="/opt/homebrew/opt/libpq/bin:$PATH"' >> ~/.zshrc
source ~/.zshrc
OR ~/bash_profile if you use it instead.

Try:

bundle install # OR
gem install pg

This works for me.

Answer 4

Well, I have tried all the solutions given above for

Can't find the PostgreSQL client library (libpq)

$ sudo su
$ env ARCHFLAGS="-arch x86_64" gem install pg

but nothing helped. For this reason, I decided to install libpq separately from Homebrew:

brew install libpq

then found a small catch though: libpq won't install itself in the /usr/local/bin directory for mac. To make that happen, you need to run:

brew link --force libpq

Which will symlink all the tools, not just libpq, into the /usr/local/bin directory. You're ready to run psql and start connecting now.

Answer 5

For my mac m1 after trying all of above solution and nothing working. I made it work by:

• Install Homebrew x86

  • brew x86 will locate on: /usr/local/Homebrew/bin/brew
  • brew arm64 locate on: /opt/homebrew/bin/brew (my current brew)

• Install libpq with arch x86 ( Since pg must be compiled with x86 libpq )

  arch --x86_64 /usr/local/Homebrew/bin/brew install libpq

• Install gem pg

  gem install pg -v '0.18.2' -- --with-pq-dir=/usr/local/Cellar/libpq/14.2 --with-pg-config=/usr/local/Cellar/libpq/14.2/bin/pg_config

Answer 6

libpq from Postgres.app will not work on ARM-based Macs, as Postgres.app is not getting released for ARM (only Universal Intel/ARM packages get released, which is just x86_64 emulation on ARM64):

~ > file /Applications/Postgres.app/Contents/Versions/13/lib/libpq.dylib
/Applications/Postgres.app/Contents/Versions/13/lib/libpq.dylib: Mach-O 64-bit dynamically linked shared library x86_64

For this reason, I decided to install libpq separately from Homebrew:

brew install libpq

Then installing pg worked with this:

gem install pg -- --with-pq-dir=/opt/homebrew/opt/libpq/

(MacOS 11.6 Big Sur on MacBook Pro 13" 2020 with Apple M1 CPU)

Answer 7

For those of you that tried the top answers and they didn't quite work, I thought I'd explain my situation and how it was fixed.

I was trying to use postgres for a Ruby project, using bundle install (and with a gem 'pg' in my gemfile), but I already had Postgres installed before, probably by using npm install pg or something like that.

I had an existing database, with data, and I was concerned that if I ran brew install postgres then it would wipe my existing data and tables.

It didn't! brew install postgres worked perfectly as suggested by @Jackie Chan

If you want to put your mind at ease though, you can back up your data as described at this link https://www.tecmint.com/backup-and-restore-postgresql-database/ e.g.

cd desktop
pg_dump -U your_db_user your_database_name >> file_containing_backup.sql

Answer 8

On Mac you can try this (works for me): gem install pg -- with-pg-include=/Library/PostgreSQL/9.5/include Fetching: pg-1.0.0.gem (100%) Building native extensions with: 'with-pg-include=/Library/PostgreSQL/9.5/include' This could take a while... Successfully installed pg-1.0.0 Parsing documentation for pg-1.0.0 Installing ri documentation for pg-1.0.0 Done installing documentation for pg after 3 seconds 1 gem installed

(this part "/Library/PostgreSQL/9.5/include" you must put your Postgres path)

Answer 9

As mentioned above this has to do with the fact of having two ruby archs on rbenv /usr/bin/ruby: Mach-O universal binary with 2 architectures: [x86_64:Mach-O 64-bit executable x86_64] [i386:Mach-O executable i386] what i had to do was simply install pg gem forcing x86_64 arch to be used with this command:

sudo env ARCHFLAGS="-arch x86_64" gem install pg

Remember to have your bash_profile up to date

Add the path of your postgres, in this case im using Postgres app (OSX) instead of brew (https://postgresapp.com/) by default this is the location:

export PATH=/Applications/Postgres.app/Contents/Versions/10/bin:$PATH

Reload bash with

sudo vi ~/.bash_profile

After doing this i was able to finally successfully install pg gem

Hope this helps!

Answer 10

This is what finally did it for me (combination of multiple solutions provided before along with other posts):

$ sudo env ARCHFLAGS="-arch x86_64" gem install pg -- with-pg-include=/Library/PostgreSQL/9.6/include/

Answer 11

I'm probably a bit late to the party here, but in my case I was using rbenv and upgrading to Ruby 2.2.3. I had to install Bundler to get mine to work, I had an old system version.

gem install bundler

Answer 12

I tried the top-rated answer here:

env ARCHFLAGS="-arch x86_64" gem install pg

But when I tried running bundle install again, it had the same error. Then I tried the entire bundle install with ARCHFLAGS like so:

ARCHFLAGS="-arch x86_64" bundle install

Worked for me! Make sure to replace x86_64 with i386 depending on what architecture you have.

Answer 13

If using Yosemite:

brew install postgres

Then:

ARCHFLAGS="-arch x86_64" gem install pg

And (optional) finally, if you want to launch autovacuum...

postgres -D /usr/local/var/postgres

Answer 14

So basically I did this ;-)

brew install postgres

Answer 15

This is how I made it to work on Mavericks. Note: I already had installed postgresql 9.3 from homebrew.

1. Update Xcode to 5.0 from App Store

2. Install command line developer tools

   xcode-select --install

3. Agree to Xcode license

   sudo xcodebuild -license

4. Install gem

   ARCHFLAGS="-arch x86_64" gem install pg

Answer 16

$ sudo su

$ env ARCHFLAGS="-arch x86_64" gem install pg

Building native extensions.  This could take a while...
Successfully installed pg-0.11.0
1 gem installed
Installing ri documentation for pg-0.11.0...
Installing RDoc documentation for pg-0.11.0...

WORKED!

Answer 17

The problem we had was pretty weird.

ruby -v # was ok (rbenv)
gem -v # was ok (rbenv)

but when we did a bundle install in fact, bundler wasn't installed for the version of ruby that was installed by rbenv, so, when we typed bundle install, it used the bundler of the system.

So before running bundle install, be sure that you have installed bundler by running

gem install bundler

Answer 18

The ARCHFLAGS answer that others have proposed will not work if you somehow ended up with a 64-bit version of postgres (which homebrew will install) and a 32-bit version of ruby. For some reason rbenv insists on building ruby 1.9.2-p290 as 32-bit for me, which makes it impossible to link against 64-bit postgres.

Check the architecture of your ruby binary with

file `which ruby`

or if using rbenv

file `rbenv which ruby`

And compare against your postgres:

file `which postgres`

If there's a mis-match you'll need to re-install postgres or ruby. With rbenv I solved this just by switching to a different version: 1.9.3-p194 instead of 1.9.2-p290.

Answer 19

Fake out gem by prefixing the appropriate environment variables. If you were installing from MacPorts, you should be able to walk through the following procedure:

% /opt/local/lib/postgresql91/bin/pg_config
BINDIR = /opt/local/lib/postgresql91/bin
DOCDIR = /opt/local/share/doc/postgresql
HTMLDIR = /opt/local/share/doc/postgresql
INCLUDEDIR = /opt/local/include/postgresql91
PKGINCLUDEDIR = /opt/local/include/postgresql91
INCLUDEDIR-SERVER = /opt/local/include/postgresql91/server
LIBDIR = /opt/local/lib/postgresql91
PKGLIBDIR = /opt/local/lib/postgresql91
LOCALEDIR = /opt/local/share/locale
MANDIR = /opt/local/share/man
SHAREDIR = /opt/local/share/postgresql91
SYSCONFDIR = /opt/local/etc/postgresql91
PGXS = /opt/local/lib/postgresql91/pgxs/src/makefiles/pgxs.mk
CONFIGURE = '--prefix=/opt/local' '--sysconfdir=/opt/local/etc/postgresql91' '--bindir=/opt/local/lib/postgresql91/bin' '--libdir=/opt/local/lib/postgresql91' '--includedir=/opt/local/include/postgresql91' '--datadir=/opt/local/share/postgresql91' '--mandir=/opt/local/share/man' '--with-includes=/opt/local/include' '--with-libraries=/opt/local/lib' '--with-openssl' '--with-bonjour' '--with-readline' '--with-zlib' '--with-libxml' '--with-libxslt' '--enable-thread-safety' '--enable-integer-datetimes' '--with-ossp-uuid' 'CC=/usr/bin/gcc-4.2' 'CFLAGS=-pipe -O2 -arch x86_64' 'LDFLAGS=-L/opt/local/lib -arch x86_64' 'CPPFLAGS=-I/opt/local/include -I/opt/local/include/ossp'
CC = /usr/bin/gcc-4.2
CPPFLAGS = -I/opt/local/include -I/opt/local/include/ossp -I/opt/local/include/libxml2 -I/opt/local/include
CFLAGS = -pipe -O2 -arch x86_64 -Wall -Wmissing-prototypes -Wpointer-arith -Wdeclaration-after-statement -Wendif-labels -Wformat-security -fno-strict-aliasing -fwrapv
CFLAGS_SL = 
LDFLAGS = -L/opt/local/lib -arch x86_64 -L/opt/local/lib -L/opt/local/lib -Wl,-dead_strip_dylibs
LDFLAGS_EX = 
LDFLAGS_SL = 
LIBS = -lpgport -lxslt -lxml2 -lssl -lcrypto -lz -lreadline -lm 
VERSION = PostgreSQL 9.1beta1

From there, pull out the LIBDIR, INCLUDEDIR, CPPFLAGS, LIBS and LDFLAGS (the one that I think will get you running is LIBDIR, however). Then you'd run:

setenv PATH /opt/local/lib/postgresql91/bin:${PATH}
sudo env LDFLAGS=-L`pg_config --libdir` CPPFLAGS=`pg_config --cppflags` gem install pg

That should do it for you. Let me know if it doesn't.

Answer 20

Solution: reinstalled PostgreSQL with Homebrew.

Answer 21

Maybe you can try this one:

ARCHFLAGS="-arch i386 -arch x86_64" gem install pg

To know the architecture of your library you can use

file /usr/local/lib/libpq.dylib 

which gave just 1 architecture in my case (installed via homebrew):

/usr/local/lib/libpq.dylib: Mach-O 64-bit dynamically linked shared library x86_64

Answer 22

I don't think you need the postgres development files, everything you need should have been included with your installer. It's more likely that the path they're installed to isn't in your environment path and therefore gem can't find them when it tries to compile pg.

You shouldn't have to run gem install pg as root, in fact if you do it's likely your PATH (root's PATH if run w/ sudo) won't contain the necessary info.

The following usually works for me:

# Might be different depending on where your installer installed postgres 8.3
export PATH=$PATH:/Library/PostgreSQL/8.3/include/
export ARCHFLAGS='-arch x86_64'
gem install pg

Answer 23

I was just having this problem when using the EnterpiseDB .dmg. If that's the same think you used, I got it to work by specifying the right architecture:

sudo env ARCHFLAGS="-arch i386" gem install pg

There are some tutorials on the web that said to specify a different architecture (like "-arch x86_64" for people who used MacPorts) but it wasn't working for me because I used the single file install.