Can't find the PostgreSQL client library (libpq) - ruby-on-rails

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

$ 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 2

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 3

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.

Answer 4

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 5

Solution: reinstalled PostgreSQL with Homebrew.

Answer 6

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 7

The error message is right there:
Can't find the PostgreSQL client library (libpq)
You can fix that by using homebrew to install it
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:$PATH"' >> ~/.zshrc
For compilers to find libpq you may need to set:
export LDFLAGS="-L/opt/homebrew/opt/libpq/lib"
export CPPFLAGS="-I/opt/homebrew/opt/libpq/include"
You can then run it:
export PATH="/opt/homebrew/opt/libpq/bin:$PATH"
gem install pg
Done.

Answer 8

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 9

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 10

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 11

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 12

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 13

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 14

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 15

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 16

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 17

This is how I made it to work on Mavericks. Note: I already had installed postgresql 9.3 from homebrew.
Update Xcode to 5.0 from App Store
Install command line developer tools
xcode-select --install
Agree to Xcode license
sudo xcodebuild -license
Install gem
ARCHFLAGS="-arch x86_64" gem install pg

Answer 18

So basically I did this ;-)
brew install postgres

Answer 19

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 20

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 21

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 22

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 23

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