gem eventmachine fatal error: 'openssl/ssl.h' file not found

$ gem install eventmachine -- --with-cppflags=-I/usr/local/opt/openssl/include                                                                                                             
Building native extensions with: '--with-cppflags=-I/usr/local/opt/openssl/include'
This could take a while...
Successfully installed eventmachine-1.0.8
1 gem installed

You can also set up bundler like this but I think that is superficial

bundle config build.eventmachine --with-cppflags=-I/usr/local/opt/openssl/include

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When using bundler and homebrew:

$ bundle config build.eventmachine --with-cppflags=-I$(brew --prefix openssl)/include
$ bundle install

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brew link --force openssl

Then:

gem install eventmachine

It also fixes:

gem install taks

bundle install

rake and rails tasks

P.S. Probably you'll need to remove and run brew install openssl again

The issue happends because Apple had removed openssl from OSX (in El Captain build)

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gem pristine eventmachine -- --with-cppflags=-I/usr/local/opt/openssl/include

pristine removes the old gem and recompiles it.

The cpp flags option allows the compiler to find the openssl headers.

If you prefer to abstract away the cpp flags argument, you can do the following:

PKG_CONFIG_PATH="$(brew --prefix openssl)/lib/pkgconfig"

You can also add the version if you like:

gem pristine eventmachine -v '1.0.4' -- --with-cppflags=-I/usr/local/opt/openssl/include

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I was trying to install v 1.0.3 and this worked for me.

gem install eventmachine -v '1.0.3' -- --with-cppflags=-I/usr/local/opt/openssl/include

These discussions were very helpful: https://github.com/eventmachine/eventmachine/issues/602

This assumes the machine already has openssl installed via brew.

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If you're installing EventMachine as a dependency of another gem, be sure to specify the correct version when you manually install the gem:

gem install eventmachine -v 1.0.5 -- --with-cppflags=-I$(brew --prefix openssl)/include

Then you can install the gem that you were originally trying to install:

gem install mailcatcher

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This solved the problem for me:

PKG_CONFIG_PATH="$(brew --prefix openssl)/lib/pkgconfig" gem install eventmachine -v "1.0.8"

Source: https://github.com/sj26/mailcatcher/issues/254

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One alternative is to add a bundler config entry for your whole user profile, like this:

cd ~
bundle config build.eventmachine --with-cppflags=-I$(brew --prefix openssl)/include

it'll create a .bundle/config file in your home directory, which is then used in all your projects when you run bundle install.

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This worked for me -

    gem install eventmachine -v '1.0.7' -- --debug --backtrace --with-cppflags=-I/usr/local/opt/openssl/include --with-ldflags=-L/usr/local/opt/openssl/lib
    Building native extensions with: '--debug --backtrace --with-cppflags=-I/usr/local/opt/openssl/include --with-ldflags=-L/usr/local/opt/openssl/lib'
    This could take a while...
    Successfully installed eventmachine-1.0.7
    Parsing documentation for eventmachine-1.0.7
    Installing ri documentation for eventmachine-1.0.7
    Done installing documentation for eventmachine after 9 seconds
    1 gem installed

NOTE:- Before I was able to successfully install this gem, I had to do a few things. These might apply to you, so listing them here -

1.) got off the corporate-VPN OR you might have to turn ON proxy settings

2.) PKG_CONFIG_PATH was set to -

echo $PKG_CONFIG_PATH
/usr/local/opt/openssl/lib/pkgconfig

3.) had to add the following to $PATH in bash_profile (in my case ~/.zshrc)

export PATH="/usr/local/opt/openssl/bin:$PATH"

4.) Also note, that contrary to some answers I got in this SO post, and also this thread on github-eventmachine, I was not able to install eventmachine

gem install eventmachine -v '1.0.7' -- --debug --backtrace --with-cppflags=-I/usr/local/include --with-ldflags=-L/usr/local/lib
Fetching: eventmachine-1.0.7.gem (100%)
Building native extensions with: '--debug --backtrace --with-cppflags=-I/usr/local/include --with-ldflags=-L/usr/local/lib'
This could take a while...
ERROR:  Error installing eventmachine:
    ERROR: Failed to build gem native extension.

It seems /usr/local/opt/openssl/include is the right location and not /usr/local/include when specifying the openssl location.

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This looks like a more recent issue: https://github.com/eventmachine/eventmachine/issues/936

I solved this problem on macOS 12.3.1 with the following:

M1 Max:

gem install eventmachine -- --with-openssl-dir=/opt/homebrew/Cellar/openssl@1.1/1.1.1n/

Intel:

gem install eventmachine -- --with-openssl-dir=/usr/local/Cellar/openssl@1.1/1.1.1n/

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For Jekyll and Fish:

gem install jekyll -- --with-cppflags=-I(brew --prefix openssl)/include

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This installed it for me:

gem install eventmachine -- --with-openssl-dir=/usr/local/opt/openssl@1.1

I got it from the eventmachine Github repo. Evidently OpenSSL tools were moved / removed from MacOS at some point.

In my case, I wanted to install something else (mailcatcher) with a dependency on eventmachine. I did this by replacing eventmachine with mailcatcher in the above command.

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