more/getting_started.rst

__ Getting Started

Contents

Introduction

Welcome to the Boost libraries! By the time you've completed this tutorial, you'll be at least somewhat comfortable with the contents of a Boost distribution and how to go about using it.

What's Here

This document is designed to be an extremely gentle introduction, so we included a fair amount of material that may already be very familiar to you. To keep things simple, we also left out some information intermediate and advanced users will probably want. At the end of this document, we'll refer you on to resources that can help you pursue these topics further.

Preliminaries

We use one typographic convention that might not be immediately obvious: italic text in examples is meant as a descriptive placeholder for something else, usually information that you'll provide. For example:

$ echo "My name is your name"

Here you're expected to imagine replacing the text “your name” with your actual name.

We identify Unix and its variants such as Linux, FreeBSD, and MacOS collectively as *nix. If you're not targeting Microsoft Windows, the instructions for *nix users will probably work for you. Cygwin users working from the Cygwin bash prompt should also follow the *nix instructions. To use your Cygwin compiler from the Windows command prompt, follow the instructions for Windows users.

Although Boost supports a wide variety of Windows compilers (including older Microsoft compilers), most instructions for Windows users cover only the Visual Studio .NET 2003 and Visual Studio 2005. We hope that gives you enough information to adapt them for your own compiler or IDE.

Get Boost

There are basically three ways to get Boost on your system:

1. Windows Installer: Boost Consulting provides an installer for Windows platforms that installs a complete Boost distribution, plus optional precompiled library binaries for Visual Studio, and (optionally) a prebuilt version of the bjam build tool.

2. Download: users of other platforms—and Windows users who prefer to build everything from scratch—can download a complete Boost distribution from SourceForge.

   __ http://sourceforge.net/project/showfiles.php?group_id=7586&package_id=8041&release_id=376197

   • Windows: Download and run boost_1_34_0.exe to unpack the distribution.¹

   • *nix: Download boost_1_34_0.tar.bz2. Then, in the directory where you want to put the Boost installation, execute

     tar --bzip2 -xf /path/to/boost_1_34_0.tar.bz2

3. Boost packages from RedHat, Debian, or some other distribution packager: these instructions may not work for you if you use 3rd party packages, because other packagers sometimes choose to break Boost up into several packages or to reorganize the directory structure of the Boost distribution.²

The Structure of a Boost Distribution

This is is a sketch of the directory structure you'll get when you unpack your Boost installation (windows users replace forward slashes with backslashes):

boost_1_34_0/ .................The “boost root directory”

index.htm .........A copy of www.boost.org starts here boost/ .........................All Boost Header files libs/ ............Tests, .cpps, docs, etc., by library³ index.html ........Library documentation starts here algorithm/ any/ array/ …more libraries… status/ .........................Boost-wide test suite tools/ ...........Utilities, e.g. bjam, quickbook, bcp more/ ..........................Policy documents, etc. doc/ ...............A subset of all Boost library docs

Header Organization

The organization of Boost library headers isn't entirely uniform, but most libraries follow a few patterns:

• Some older libraries and most very small libraries place all public headers directly into boost/.
• Most libraries' public headers live in a subdirectory of boost/ named after the library. For example, you'll find the Type Traits Library's is_void.hpp header in boost/type_traits/is_void.hpp.
• Some libraries have an “aggregate header” in boost/ that #includes all of the library's other headers. For example, Boost.Python's aggregate header is boost/python.hpp.
• Most libraries place private headers in a subdirectory called detail/ or aux_/. Don't look in these directories and expect to find anything you can use.

A few things are worth noting right off the bat:

1. The path to the “boost root directory” is sometimes referred to as $BOOST_ROOT in documentation and mailing lists. If you used the Windows installer, that will usually be C:\ProgramFiles\boost\boost_1_34_0.

2. To compile anything in Boost, you need a directory containing the boost/ subdirectory in your #include path. For most compilers, that means adding

   -I/path/to/boost_1_34_0

   to the command line. Specific steps for setting up #include paths in Microsoft Visual Studio follow later in this document; if you use another IDE, please consult your product's documentation for instructions.

3. Since all of Boost's header files have the .hpp extension, and live in the boost/ subdirectory of the boost root, your Boost #include directives will look like:

   #include <boost/whatever.hpp>

   or

   #include "boost/whatever.hpp"

depending on your religion as regards the use of angle bracket includes. Even Windows users can use forward slashes in #include directives; your compiler doesn't care.

4. Don't be distracted by the doc/ subdirectory; it only contains a subset of the Boost documentation. Start with libs/index.html if you're looking for the whole enchilada.

Header-Only Libraries

The first thing many people want to know is, “how do I build Boost?” The good news is that often, there's nothing to build.

Nothing to Build

Most Boost libraries are header-only: they consist entirely of header files containing templates and inline functions, and require no separately-compiled library binaries or special treatment when linking.

The only Boost libraries that can't be used without separate compilation are:

• Boost.Filesystem
• Boost.IOStreams
• Boost.ProgramOptions
• Boost.Python
• Boost.Regex
• Boost.Serialization
• Boost.Signals
• Boost.Test
• Boost.Thread
• Boost.Wave

The DateTime library has a separately-compiled component that is only needed if you're using its to/from_string and/or serialization features or if you're targeting Visual C++ 6.x or Borland. The Graph library also has a separately-compiled part, but you won't need it unless you intend to parse GraphViz files.

Build a Simple Program Using Boost

To keep things simple, let's start by using a header-only library. The following program reads a sequence of integers from standard input, uses Boost.Lambda to multiply each number by three, and writes them to standard output:

#include <boost/lambda/lambda.hpp>
#include <iostream>
#include <iterator>
#include <algorithm>

int main() 
{
    using namespace boost::lambda;
    typedef std::istream_iterator<int> in;

    std::for_each( 
        in(std::cin), in(), std::cout << (_1 * 3) << " " );
}

Copy the text of this program into a file called example.cpp.

Build on *nix

In the directory where you saved example.cpp, issue the following command:

c++ -I /path/to/boost_1_34_0 example.cpp -o example

To test the result, type:

echo 1 2 3 | ./example

next...__

Build from the Visual Studio Command Prompt

From your computer's Start menu, if you are a Visual Studio 2005 user, select

All Programs > Microsoft Visual Studio 2005 > Visual Studio Tools > Visual Studio 2005 Command Prompt

or, if you're a Visual Studio .NET 2003 user, select

All Programs > Microsoft Visual Studio .NET 2003 > Visual Studio .NET Tools > Visual Studio .NET 2003 Command Prompt

to bring up a special command prompt window set up for the Visual Studio compiler. In that window, type the following command and hit the return key:

cl /EHsc /Ipath\to\boost_1_34_0 path\to\example.cpp

To test the result, type:

echo 1 2 3 | example

next...__

Build in the Visual Studio IDE

• From Visual Studio's File menu, select New > Project…
• In the left-hand pane of the resulting New Project dialog, select Visual C++ > Win32.
• In the right-hand pane, select Win32 Console Application (VS8.0) or Win32 Console Project (VS7.1).
• In the name field, enter “example”
• Right-click example in the Solution Explorer pane and select Properties from the resulting pop-up menu
• In Configuration Properties > C/C++ > General > Additional Include Directories, enter the path to the Boost root directory, e.g. C:\ProgramFiles\boost\boost_1_34_0.
• In Configuration Properties > C/C++ > Precompiled Headers, change Use Precompiled Header (/Yu) to Not Using Precompiled Headers.⁴
• Replace the contents of the example.cpp generated by the IDE with the example code above.
• From the Build menu, select Build Solution.

To test your application, hit the F5 key and type the following into the resulting window, followed by the return key:

1 2 3

Then hold down the control key and press "Z", followed by the return key.

Errors and Warnings

Don't be alarmed if you see compiler warnings from Boost headers. We try to eliminate them, but doing so isn't always practical. ⁵

Errors are another matter. If you're seeing compilation errors at this point in the tutorial, check to be sure you've copied the example program correctly and that you've correctly identified the Boost root directory.

Get Boost Library Binaries

If you want to use any of the separately-compiled Boost libraries, you'll need library binaries.

Install Visual Studio Binaries

The Windows installer supplied by Boost Consulting will download and install pre-compiled binaries into the lib\ subdirectory of the boost root, typically C:\ProgramFiles\boost\boost_1_34_0\lib\.

next...__

Build and Install *nix Binaries

Issue the following commands in the shell (don't type $; it represents the shell's prompt):

$ cd /path/to/boost_1_34_0 $ ./configure --help

Select your configuration options and invoke ./configure again. Unless you have write permission in your system's /usr/local/ directory, you'll probably want to at least use

$ ./configure --prefix=path/to/installation/prefix

to install somewhere else. Finally,

$ make install

which will leave Boost binaries in the lib/ subdirectory of your installation prefix. You will also find a copy of the Boost headers in the include/ subdirectory of the installation prefix, so you can henceforth use that directory as an #include path in place of the Boost root directory.

next...__

Build and Install Other Binaries

If you're not using Visual C++ 7.1 or 8.0, or you're a *nix user who wants want to build with a toolset other than your system's default, or if you want a nonstandard variant build of Boost (e.g. optimized, but with debug symbols), you'll need to use Boost.Build to create your own binaries.

Boost.Build is a text-based system for developing, testing, and installing software. To use it, you'll need an executable called bjam.

Get bjam

bjam is the command-line tool that drives the Boost Build system. To build Boost binaries, you'll invoke bjam from the Boost root.

Boost provides pre-compiled bjam executables_ for a variety of platforms. Alternatively, you can build bjam yourself using these instructions.

Identify Your Toolset

First, find the toolset corresponding to your compiler in the following table.

Toolset Name	Vendor	Notes
acc	Hewlett Packard	Only very recent versions are known to work well with Boost
borland	Borland
como	Comeau Computing	Using this toolset may require configuring another toolset to act as its backend
cw	Metrowerks/FreeScale	The CodeWarrior compiler. We have not tested versions of this compiler produced since it was sold to FreeScale.
dmc	Digital Mars	As of this Boost release, no version of dmc is known to handle Boost well.
darwin	Apple Computer	Apple's version of the GCC toolchain with support for Darwin and MacOS X features such as frameworks.
gcc	The Gnu Project	Includes support for Cygwin and MinGW compilers.
hp_cxx	Hewlett Packard	Targeted at the Tru64 operating system.
intel	Intel
kylix	Borland
msvc	Microsoft
qcc	QNX Software Systems
sun	Sun	Only very recent versions are known to work well with Boost.
vacpp	IBM	The VisualAge C++ compiler.

If you have multiple versions of a particular compiler installed, you can apend the version number to the toolset name, preceded by a hyphen, e.g. msvc-7.1 or gcc-3.4.

Note

if you built bjam yourself, you may have selected a toolset name for that purpose, but that does not affect this step in any way; you still need to select a Boost.Build toolset from the table.

Select a Build Directory

Boost.Build will place all intermediate files it generates while building into the build directory. If your Boost root directory is writable, this step isn't strictly necessary: by default Boost.Build will create a bin.v2/ subdirectory for that purpose in your current working directory.

Invoke bjam

Change your current directory to the Boost root directory and invoke bjam as follows:

bjam --build-dir=build-directory_ \

--toolset=toolset-name_ stage

For example, on Windows, your session might look like:

C:WINDOWS> cd C:\ProgramFiles\boost\boost_1_34_0 C:\ProgramFiles\boost\boost_1_34_0> bjam \ --build-dir=%TEMP%\build-boost \ --toolset=msvc stage

And on Unix:

$ cd ~/boost_1_34_0 $ bjam --build-dir=~/build-boost --prefix=~/boost

In either case, Boost.Build will place the Boost binaries in the stage/ subdirectory of your build directory.

Note

bjam is case-sensitive; it is important that all the parts shown in bold type above be entirely lower-case.

For a description of other options you can pass when invoking bjam, type:

bjam --help

Expected Build Output

During the process of building Boost libraries, you can expect to see some messages printed on the console. These may include

• Notices about Boost library configuration—for example, the Regex library outputs a message about ICU when built without Unicode support, and the Python library may be skipped without error (but with a notice) if you don't have Python installed.

• Messages from the build tool that report the number of targets that were built or skipped. Don't be surprised if those numbers don't make any sense to you; there are many targets per library.

• Build action messages describing what the tool is doing, which look something like:

  toolset-name.c++ long/path/to/file/being/built

• Compiler warnings.

In Case of Build Errors

The only error messages you see when building Boost—if any—should be related to the IOStreams library's support of zip and bzip2 formats as described here. Install the relevant development packages for libz and libbz2 if you need those features. Other errors when building Boost libraries are cause for concern.

If it seems like the build system can't find your compiler and/or linker, consider setting up a user-config.jam file as described in the Boost.Build documentation. If that isn't your problem or the user-config.jam file doesn't work for you, please address questions about configuring Boost for your compiler to the Boost.Build mailing list.

Link Your Program to a Boost Library

To demonstrate linking with a Boost binary library, we'll use the following simple program that extracts the subject lines from emails. It uses the Boost.Regex library, which has a separately-compiled binary component. :

#include <boost/regex.hpp>
#include <iostream>
#include <string>

int main()
{
    std::string line;
    boost::regex pat( "^Subject: (Re: |Aw: )*(.*)" );

    while (std::cin)
    {
        std::getline(std::cin, line);
        boost::smatch matches;
        if (boost::regex_match(line, matches, pat))
            std::cout << matches[2] << std::endl;
    }
}

There are two main challenges associated with linking:

1. Tool configuration, e.g. choosing command-line options or IDE build settings.
2. Identifying the library binary, among all the build variants, whose compile configuration is compatible with the rest of your project.

Note

Boost.Python users should read that library's own build documentation as there are several library-specific issues to consider.

Link to a Boost Library on Windows

Most Windows compilers and linkers have so-called “auto-linking support,” which eliminates the second challenge. Special code in Boost header files detects your compiler options and uses that information to encode the name of the correct library into your object files; the linker selects the library with that name from the directories you've told it to search.

Link to a Boost Library from the Visual Studio Command Prompt

For example, we can compile and link the above program from the Visual C++ command-line by simply adding the bold text below to the command line we used earlier, assuming your Boost binaries are in C:\ProgramFiles\boost\boost_1_34_0\lib:

cl /EHsc /I path\to\boost_1_34_0 example.cpp \

/link /LIBPATH: C:\Program Files\boost\boost_1_34_0\lib

next...__

Link to a Boost Library in the Visual Studio IDE

Starting with the header-only example project we created earlier:

1. Right-click example in the Solution Explorer pane and select Properties from the resulting pop-up menu
2. In Configuration Properties > Linker > Additional Library Directories, enter the path to the Boost binaries, e.g. C:\ProgramFiles\boost\boost_1_34_0\lib\.
3. From the Build menu, select Build Solution.

next...__

Link to a Boost Library On *nix

There are two main ways to link to libraries:

1. You can specify the full path to each library:

   $ c++ -I /path/to/boost_1_34_0 example.cpp -o example \

   ~/boost/lib/libboost_regex-gcc-3.4-mt-d-1_34.a

2. You can separately specify a directory to search (with -Ldirectory) and a library name to search for (with -llibrary,⁶ dropping the filename's leading lib and trailing suffix (.a in this case):

   $ c++ -I /path/to/boost_1_34_0 example.cpp -o example \

   -L~/boost/lib/ -lboost_regex-gcc-3.4-mt-d-1_34

   As you can see, this method is just as terse as method A for one library; it really pays off when you're using multiple libraries from the same directory. Note, however, that if you use this method with a library that has both static (.a) and dynamic (.so) builds, the system may choose one automatically for you unless you pass a special option such as -static on the command line.

In both cases above, the bold text is what you'd add to the command lines we explored earlier.

Library Naming

When auto-linking is not available, you need to know how Boost binaries are named so you can choose the right one for your build configuration. Each library filename is composed of a common sequence of elements that describe how it was built. For example, libboost_regex-vc71-mt-d-1_34.lib can be broken down into the following elements:

lib

Prefix: except on Microsoft Windows, every Boost library name begins with this string. On Windows, only ordinary static libraries use the lib prefix; import libraries and DLLs do not.⁷

boost_regex

Library name: all boost library filenames begin with boost_.

-vc71

Toolset tag: identifies the toolset and version used to build the binary.

-mt

Threading tag: indicates that the library was built with multithreading support enabled. Libraries built without multithreading support can be identified by the absence of -mt.

-d

ABI tag: encodes details that affect the library's interoperability with other compiled code. For each such feature, a single letter is added to the tag:

Key	Use this library when:
s	linking statically to the C++ standard library and compiler runtime support libraries.
g	using debug versions of the standard and runtime support libraries.
y	using a special debug build of Python.
d	building a debug version of your code.8
p	using the STLPort standard library rather than the default one supplied with your compiler.
n	using STLPort's deprecated “native iostreams” feature.9

For example, if you build a debug version of your code for use with debug versions of the static runtime library and the STLPort standard library in “native iostreams” mode, the tag would be: -sgdpn. If none of the above apply, the ABI tag is ommitted.

-1_34

Version tag: the full Boost release number, with periods replaced by underscores. For example, version 1.31.1 would be tagged as "-1_31_1".

.lib

Extension: determined according to the operating system's usual convention. On most *nix platforms the extensions are .a and .so for static libraries (archives) and shared libraries, respectively. On Windows, .dll indicates a shared library and—except for static libraries built by gcc toolset, whose names always end in .a— .lib indicates a static or import library. Where supported by *nix toolsets, a full version extension is added (e.g. ".so.1.34") and a symbolic link to the library file, named without the trailing version number, will also be created.

Test Your Program

To test our subject extraction, we'll filter the following text file. Copy it out of your browser and save it as jayne.txt:

To: George Shmidlap
From: Rita Marlowe
Subject: Will Success Spoil Rock Hunter?
---
See subject.

Test Your Program on Microsoft Windows

In a command prompt window, type:

path\to\compiled\example < path\to\jayne.txt

The program should respond with the email subject, “Will Success Spoil Rock Hunter?”

Test Your Program on *nix

If you linked to a shared library, you may need to prepare some platform-specific settings so that the system will be able to find and load it when your program is run. Most platforms have an environment variable to which you can add the directory containing the library. On many platforms (Linux, FreeBSD) that variable is LD_LIBRARY_PATH, but on MacOS it's DYLD_LIBRARY_PATH, and on Cygwin it's simply PATH. In most shells other than csh and tcsh, you can adjust the variable as follows (again, don't type the $—that represents the shell prompt):

$ VARIABLE_NAME=path/to/lib/directory:${VARIABLE_NAME} $ export VARIABLE_NAME

On csh and tcsh, it's

$ setenv VARIABLE_NAME path/to/lib/directory:${VARIABLE_NAME}

Once the necessary variable (if any) is set, you can run your program as follows:

$ path/to/compiled/example < path/to/jayne.txt

The program should respond with the email subject, “Will Success Spoil Rock Hunter?”

Conclusion and Further Resources

This concludes your introduction to Boost and to integrating it with your programs. As you start using Boost in earnest, there are surely a few additional points you'll wish we had covered. One day we may have a “Book 2 in the Getting Started series” that addresses them. Until then, we suggest you pursue the following resources. If you can't find what you need, or there's anything we can do to make this document clearer, please post it to the Boost Users' mailing list.

• Boost.Build reference manual
• Boost.Jam reference manual
• Boost Users' mailing list
• Boost.Build mailing list
• Boost.Build Wiki

Onward

Good luck, and have fun!

-- the Boost Developers

Appendix: Using command-line tools in Windows

In Windows, a command-line tool is invoked by typing its name, optionally followed by arguments, into a Command Prompt window and pressing the Return (or Enter) key.

To open Command Prompt, click the Start menu button, click Run, type “cmd”, and then click OK.

All commands are executed within the context of a current directory in the filesystem. To set the current directory, type:

cd path\to\some\directory

followed by Return. For example,

cd C:\ProgramFiles\boost\boost_1_34_0

One way to name a directory you know about is to write

%HOMEDRIVE%%HOMEPATH%\directory-name

which indicates a sibling folder of your “My Documents” folder.

Long commands can be continued across several lines by typing backslashes at the ends of all but the last line. Many of the examples on this page use that technique to save horizontal space.

---

---

1. If you prefer not to download executable programs, download boost_1_34_0.zip and use an external tool to decompress it. We don't recommend using Windows' built-in decompression as it can be painfully slow for large archives.↩︎

2. If developers of Boost packages would like to work with us to make sure these instructions can be used with their packages, we'd be glad to help. Please make your interest known to the Boost developers' list.↩︎

3. If you used the Windows installer from Boost Consulting and deselected “Source and Documentation” (it's selected by default), you won't see the libs/ subdirectory. That won't affect your ability to use precompiled binaries, but you won't be able to rebuild libraries from scratch.↩︎

4. There's no problem using Boost with precompiled headers; these instructions merely avoid precompiled headers because it would require Visual Studio-specific changes to the source code used in the examples.↩︎

5. Remember that warnings are specific to each compiler implementation. The developer of a given Boost library might not have access to your compiler. Also, some warnings are extremely difficult to eliminate in generic code, to the point where it's not worth the trouble. Finally, some compilers don't have any source code mechanism for suppressing warnings.↩︎

6. That option is a dash followed by a lowercase “L” character, which looks very much like a numeral 1 in some fonts.↩︎

7. This convention distinguishes the static version of a Boost library from the import library for an identically-configured Boost DLL, which would otherwise have the same name.↩︎

8. These libraries were compiled without optimization or inlining, with full debug symbols enabled, and without NDEBUG #defined. All though it's true that sometimes these choices don't affect binary compatibility with other compiled code, you can't count on that with Boost libraries.↩︎

9. This feature of STLPort is deprecated because it's impossible to make it work transparently to the user; we don't recommend it.↩︎