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# The Ten-Minute Guide to Using qmake

## Creating a Project File

`qmake` uses information stored in project (.pro) files to determine what should go in the makefiles it generates.

A basic project file contains information about the application, for example, which files are needed to compile the application, and which configuration settings to use.

Here's a simple example project file:

        SOURCES = hello.cpp
        HEADERS = hello.h
        CONFIG += qt warn_on release

We'll provide a brief line-by-line explanation, deferring the detail until later on in the manual.

        SOURCES = hello.cpp

This line specifies the source files that implement the application. In this case there is just one file, `hello.cpp`. Most applications require multiple files; this situation is dealt with by listing all the files on the same line space separated, like this:

        SOURCES = hello.cpp main.cpp

Alternatively, each file can be listed on a separate line, by escaping the newlines, like this:

        SOURCES = hello.cpp \
                  main.cpp

A more verbose approach is to list each file separately, like this:

        SOURCES += hello.cpp
        SOURCES += main.cpp

This approach uses "+=" rather than "=" which is safer, because it always adds a new file to the existing list rather than replacing the list.

The HEADERS line is used to specify the header files created for use by the application, e.g.

        HEADERS += hello.h

Any of the approaches used to list source files may be used for header files.

The CONFIG line is used to give `qmake` information about the application's configuration.

        CONFIG += qt warn_on release

The "+=" is used here, because we add our configuration options to any that are already present. This is safer than using "=" which replaces all options with just those specified.

The `qt` part of the CONFIG line tells `qmake` that the application is built using Qt. This means that `qmake` will link against the Qt libraries when linking and add in the neccesary include paths for compiling.

The `warn_on` part of the CONFIG line tells `qmake` that it should set the compiler flags so that warnings are output.

The `release` part of the CONFIG line tells `qmake` that the application must be built as a release application. During development, programmers may prefer to replace `release` with `debug`, which is discussed later.

Project files are plain text (i.e. use an editor like notepad, vim or xemacs) and must be saved with a `.pro` extension. The name of the application's executable will be the same as the project file's name, but with an extension appropriate to the platform. For example, a project file called `hello.pro` will produce `hello.exe` on Windows and `hello` on Unix.

## Generating a Makefile

When you have created your project file it is very easy to generate a makefile, all you need to do is go to where you have created your project file and type:

Makefiles are generated from the `.pro` files like this:

        qmake -o Makefile hello.pro

For Visual Studio users, `qmake` can also generate `.dsp` files, for example:

        qmake -t vcapp -o hello.dsp hello.pro