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NAME

apxs — APache eXtenSion tool

SYNOPSIS

DESCRIPTION

apxs is a tool for building and installing extension modules for the Apache HyperText Transfer Protocol (HTTP) server, httpd(8). This is achieved by building a Dynamic Shared Object (DSO) from one or more source or object files which can then be loaded into httpd at runtime via the LoadModule directive from mod_so. To use this extension mechanism, your platform has to support the DSO feature and the httpd binary has to be built with the mod_so module. The apxs tool automatically complains if this is not the case. Check by manually running the following command:

The module mod_so should be part of the displayed list. If these requirements are fulfilled, httpd's functionality can be extended by installing modules with the DSO mechanism, with the help of the apxs tool:

# apxs -i -a -c mod_foo.c
cc -O2 -pipe -DDEV_RANDOM=/dev/arandom -DMOD_SSL=208116 -DEAPI -DUSE_EXPAT -I../lib/expat-lite -DUSE_SETUSERCONTEXT -fPIC -DSHARED_MODULE -I/usr/lib/apache/include  -c mod_foo.c
[activating module `foo' in /var/www/conf/httpd.conf]
cp mod_foo.so /usr/lib/apache/modules/mod_foo.so
chmod 755 /usr/lib/apache/modules/mod_foo.so
cp /var/www/conf/httpd.conf /var/www/conf/httpd.conf.bak
cp /var/www/conf/httpd.conf.new /var/www/conf/httpd.conf
rm /var/www/conf/httpd.conf.new
# apachectl restart
/usr/sbin/apachectl restart: httpd not running, trying to start
/usr/sbin/apachectl restart: httpd started

The argument file can be any C source file (.c), an object file (.o), or even a library archive (.a). The apxs tool automatically recognizes these extensions and automatically uses the C source files for compilation, whereas it just uses the object and archive files for the linking phase. But when using such pre-compiled objects, make sure they are compiled for Position Independent Code (PIC) to be able to use them for a DSO. For instance, with cc(1) just use -fpic. For other C compilers, please consult their manual pages or watch for the flags apxs uses to compile the object files.

For more details about DSO support in Apache, first read the background information about DSO in htdocs/manual/dso.html, then read the documentation of mod_so.

The options are as follows:

-A

Same as the -a option but the created LoadModule directive is prefixed with a hash sign (#), i.e. the module is just prepared for later activation but initially disabled.

-a

This activates the module by automatically adding a corresponding LoadModule line to Apache's httpd.conf configuration file, or by enabling it if it already exists.

-c

Compile. This option first compiles the C source files (.c) of file ... into corresponding object files (.o) and then builds a DSO in dsofile by linking these object files plus the remaining object files (.o and .a) of file ... If no -o option is specified, the output file is guessed from the first filename in file ... and thus usually defaults to mod_name.so

-D variable[=value]

This option is directly passed through to the compilation command(s). Use this to add your own defines to the build process.

-e

Edit. This option can be used with the -a and -A options to edit the configuration file, /var/www/conf/httpd.conf, without attempting to install the module.

-g

Template generation. This option generates a subdirectory name (see the -n option) and two files: a sample module source file named mod_name.c, which can be used as a template for creating your own modules or as a quick start for playing with the apxs mechanism, and a corresponding Makefile for even easier building and installing of this module.

-I incdir

This option is directly passed through to the compilation command(s). Use this to add your own include directories to search to the build process.

-i

Install. This option installs one or more DSOs into the server's libexec directory.

-L libdir

This option is directly passed through to the linker command. Use this to add your own library directories to search to the build process.

-l libname

This option is directly passed through to the linker command. Use this to add your own libraries to search to the build process.

-n name

This explicitly sets the module name for the -i (install) and -g (template generation) option. Use this to explicitly specify the module name. For option -g this is required; for option -i, apxs tries to determine the name from the source or (as a fallback) at least by guessing it from the filename.

-o dsofile

Explicitly specifies the filename of the created DSO file. If not specified and the name cannot be guessed from the file ... list, the fallback name mod_unknown.so is used.

-q

Query. This option performs a query for apxs's knowledge about certain settings. The query parameters can be one or more of the following variable names:

CC              TARGET
CFLAGS          SBINDIR
CFLAGS_SHLIB    INCLUDEDIR
LD_SHLIB        LIBEXECDIR
LDFLAGS_SHLIB   SYSCONFDIR
LIBS_SHLIB      PREFIX

Use this for manually determining settings. For instance, use the following inside your own Makefiles if you need manual access to Apache's C header files:

INC=-I`apxs -q INCLUDEDIR`

-S variable=value

This option changes the apxs settings described above.

-Wc,compiler-flags

This option passes compiler-flags as additional flags to the compiler command. Use this to add local compiler-specific options. This option may be specified multiple times in order to pass multiple flags.

-Wl,linker-flags

This option passes linker-flags as additional flags to the linker command. Use this to add local linker-specific options. This option may be specified multiple times in order to pass multiple flags.

EXAMPLES

Assume you have a module named “mod_foo.c” available which should extend httpd's functionality. To accomplish this, first compile the C source into a DSO suitable for loading into httpd at runtime via the following command:

# apxs -c mod_foo.c
cc -O2 -pipe -DDEV_RANDOM=/dev/arandom -DMOD_SSL=208116 -DEAPI -DUSE_EXPAT -I../lib/expat-lite -DUSE_SETUSERCONTEXT -fPIC -DSHARED_MODULE -I/usr/lib/apache/include  -c mod_foo.c
cc -shared -fPIC -DSHARED_MODULE -o mod_foo.so mod_foo.o

Then a LoadModule directive has to be added to httpd's configuration file to load the DSO. To simplify this step, apxs provides an automatic way to install the DSO in the “libexec” directory and update the httpd.conf file accordingly. This can be achieved by running the following:

$ apxs -i -a mod_foo.so
[activating module `foo' in /var/www/conf/httpd.conf]
cp mod_foo.so /usr/lib/apache/modules/mod_foo.so
chmod 755 /usr/lib/apache/modules/mod_foo.so
cp /var/www/conf/httpd.conf /var/www/conf/httpd.conf.bak
cp /var/www/conf/httpd.conf.new /var/www/conf/httpd.conf
rm /var/www/conf/httpd.conf.new

This way a line such as the following is added to the configuration file:

If you want the module added to the configuration file without it being enabled, use the -A option instead:

For a quick test of the apxs mechanism, create a sample module template plus a corresponding Makefile via:

# apxs -g -n foo
Creating [DIR]  foo
Creating [FILE] foo/Makefile
Creating [FILE] foo/mod_foo.c

The sample module can then be immediately compiled into a DSO and loaded into the httpd server:

$ cd foo
$ make all reload
apxs -c    mod_foo.c
cc -O2 -pipe -DDEV_RANDOM=/dev/arandom -DMOD_SSL=208116 -DEAPI -DUSE_EXPAT -I../lib/expat-lite -DUSE_SETUSERCONTEXT -fPIC -DSHARED_MODULE -I/usr/lib/apache/include  -c mod_foo.c
cc -shared -fPIC -DSHARED_MODULE -o mod_foo.so mod_foo.o
apxs -i -a -n 'foo' mod_foo.so
[activating module `foo' in /var/www/conf/httpd.conf]
cp mod_foo.so /usr/lib/apache/modules/mod_foo.so
chmod 755 /usr/lib/apache/modules/mod_foo.so
cp /var/www/conf/httpd.conf /var/www/conf/httpd.conf.bak
cp /var/www/conf/httpd.conf.new /var/www/conf/httpd.conf
rm /var/www/conf/httpd.conf.new
apachectl restart
/usr/sbin/apachectl restart: httpd not running, trying to start
/usr/sbin/apachectl restart: httpd started

apxs can even be used to compile complex modules outside the httpd source tree, like PHP3, because apxs automatically recognizes C source files and object files.

$ cd php3
$ ./configure --with-shared-apache=../apache-1.3
$ apxs -c -o libphp3.so mod_php3.c libmodphp3-so.a
gcc -fpic -DSHARED_MODULE -I/tmp/apache/include  -c mod_php3.c
ld -Bshareable -o libphp3.so mod_php3.o libmodphp3-so.a

Only C source files are compiled, while remaining object files are used for the linking phase.

SEE ALSO

cc(1), apachectl(8), httpd(8)