How to determine the Boost version on a system?

Boost installed on OS X using homebrew has desired version.hpp file in /usr/local/Cellar/boost/<version>/include/boost/version.hpp (note, that the version is already mentioned in path).

I guess the fastest way to determine version on any UNIX-like system will be to search for boost in /usr:

find /usr -name "boost"

As to me, you can first(find version.hpp the version variable is in it, if you know where it is(in ubuntu it usually in /usr/include/boost/version.hpp by default install)):

 locate `boost/version.hpp`

Second show it's version by:

 grep BOOST_LIB_VERSION /usr/include/boost/version.hpp

or

  grep BOOST_VERSION /usr/include/boost/version.hpp.

As to me, I have two version boost installed in my system. Output as below:

xy@xy:~$ locate boost/version.hpp |grep boost

/home/xy/boost_install/boost_1_61_0/boost/version.hpp
/home/xy/boost_install/lib/include/boost/version.hpp
/usr/include/boost/version.hpp

xy@xy:~$ grep BOOST_VERSION /usr/include/boost/version.hpp
#ifndef BOOST_VERSION_HPP
#define BOOST_VERSION_HPP
//  BOOST_VERSION % 100 is the patch level
//  BOOST_VERSION / 100 % 1000 is the minor version
//  BOOST_VERSION / 100000 is the major version
#define BOOST_VERSION 105800
//  BOOST_LIB_VERSION must be defined to be the same as BOOST_VERSION

# or this way more readable
xy@xy:~$ grep BOOST_LIB_VERSION /usr/include/boost/version.hpp
//  BOOST_LIB_VERSION must be defined to be the same as BOOST_VERSION
#define BOOST_LIB_VERSION "1_58"

Show local installed version:

xy@xy:~$ grep BOOST_LIB_VERSION /home/xy/boost_install/lib/include/boost/version.hpp
//  BOOST_LIB_VERSION must be defined to be the same as BOOST_VERSION
#define BOOST_LIB_VERSION "1_61"

@Vertexwahns answer, but written in bash. For the people who are lazy:

boost_version=$(cat /usr/include/boost/version.hpp | grep define | grep "BOOST_VERSION " | cut -d' ' -f3)
echo "installed boost version: $(echo "$boost_version / 100000" | bc).$(echo "$boost_version / 100 % 1000" | bc).$(echo "$boost_version % 100 " | bc)"

Gives me installed boost version: 1.71.0

I stugeled to find out the boost version number in bash.

Ended up doing following, which stores the version code in a variable, supressing the errors. This uses the example from maxschlepzig in the comments of the accepted answer. (Can not comment, don't have 50 Rep)

I know this has been answered long time ago. But I couldn't find how to do it in bash anywhere. So I thought this might help someone with the same problem. Also this should work no matter where boost is installed, as long as the comiler can find it. And it will give you the version number that is acutally used by the comiler, when you have multiple versions installed.

{
VERS=$(echo -e '#include <boost/version.hpp>\nBOOST_VERSION' | gcc -s -x c++ -E - | grep "^[^#;]")
} &> /dev/null

Another way to get current boost version (Linux Ubuntu):

~$ dpkg -s libboost-dev | grep Version
Version: 1.58.0.1ubuntu1

Ref: https://www.osetc.com/en/how-to-install-boost-on-ubuntu-16-04-18-04-linux.html

cat /usr/local/include/boost/version.hpp | grep BOOST_LIB_VERSION

If one installed boost on macOS via Homebrew, one is likely to see the installed boost version(s) with:

ls /usr/local/Cellar/boost*