apxs - APache eXtenSion tool

apxs -g [ -S"variable=value ] -n name

apxs -q [ -S"variable=value ] query ...

apxs -c [ -S"variable=value ] [ -o dsofile ] [ -I incdir ] [ -D variable[=value] ] [ -L libdir ] [ -l libname ] [ -Wc,compiler-flags ] [ -Wl,linker-flags ] files ...

apxs -i [ -S"variable=value ] [ -n name ] [ -a ] [ -A ] dsofile ...

apxs -e [ -S"variable=value ] [ -n name ] [ -a ] [ -A ] dsofile ...

apxs is a tool for building and installing extension modules for the Apache HyperText Transfer Protocol (HTTP) server. This is achieved by building a Dynamic Shared Object (DSO) from one or more source or object files which then can be loaded into the Apache server under runtime via the LoadModule directive from mod_so.

So to use this extension mechanism, your platform has to support the DSO feature and your Apache apache-perl binary has to be built with the mod_so module. The apxs tool automatically complains if this is not the case. You can check this yourself by manually running the command

  $ apache-perl -l

The module mod_so should be part of the displayed list. If these requirements are fulfilled, you can easily extend your Apache server's functionality by installing your own modules with the DSO mechanism by the help of this apxs tool:

  $ apxs -i -a -c mod_foo.c
  gcc -fpic -DSHARED_MODULE -I/path/to/apache/include -c mod_foo.c
  ld -Bshareable -o mod_foo.so mod_foo.o
  cp mod_foo.so /path/to/apache/libexec/mod_foo.so
  chmod 755 /path/to/apache/libexec/mod_foo.so
  [activating module `foo' in /path/to/apache/etc/httpd.conf]
  $ apachectl restart
  /path/to/apache/sbin/apachectl restart: httpd not running, trying to start
  [Tue Mar 31 11:27:55 1998] [debug] mod_so.c(3): loaded module foo_module
  /path/to/apache/sbin/apachectl restart: httpd started
  $ _

The arguments files can be any C source file (.c), a 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 while 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 Independend Code (PIC) to be able to use them for a DSO. For instance with GCC you always just have to use -fpic. For other C compilers please consult its manual page 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.

Common options:

-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 the apxs tool tries to determine the name from the source or (as a fallback) at least by guessing it from the filename.

Query options:

-q

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

  INC=-I`apxs -q INCLUDEDIR`

inside your own Makefiles if you need manual access to Apache's C header files.

Configuration options:

-S variable=value

This option changes the apxs settings described above.

Template Generation options:

-g

This generates a subdirectory name (see option -n) and there 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.

DSO compilation options:

-c

This indicates the compilation operation. It first compiles the C source files (.c) of files 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 files If no -o option is specified the output file is guessed from the first filename in files and thus usually defaults to mod_name.so

-o dsofile

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

-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.

-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.

-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.

-Wc,compiler-flags

This option passes compiler-flags as additional flags to the compiler command. Use this to add local compiler-specific options.

-Wl,linker-flags

This option passes linker-flags as additional flags to the linker command. Use this to add local linker-specific options.

DSO installation and configuration options:

-i

This indicates the installation operation and installs one or more DSOs into the server's libexec directory.

-a

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

-A

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

-e

This indicates the editing operation, which can be used with the -a and -A options similarly to the -i operation to edit Apache's apache-perl.conf configuration file without attempting to install the module.

Assume you have an Apache module named mod_foo.c available which should extend Apache's server functionality. To accomplish this you first have to compile the C source into a DSO suitable for loading into the Apache server under runtime via the following command:

  $ apxs -c mod_foo.c
  gcc -fpic -DSHARED_MODULE -I/path/to/apache/include -c mod_foo.c
  ld -Bshareable -o mod_foo.so mod_foo.o
  $ _

Then you have to update the Apache configuration by making sure a LoadModule directive is present to load this DSO. To simplify this step apxs provides an automatic way to install the DSO in the "libexec" directory and updating the apache-perl.conf file accordingly. This can be achieved by running:

  $ apxs -i -a mod_foo.c
  cp mod_foo.so /path/to/apache/libexec/mod_foo.so
  chmod 755 /path/to/apache/libexec/mod_foo.so
  [activating module `foo' in /path/to/apache/etc/httpd.conf]
  $ _

This way a line named

  LoadModule foo_module libexec/mod_foo.so

is added to the configuration file if still not present. If you want to have this operation to be disabled, use the -A option, i.e.

  $ apxs -i -A mod_foo.c

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

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

Then you can immediately compile this sample module into a DSO and load it into the Apache server:

  $ cd foo
  $ make all reload
  apxs -c mod_foo.c
  gcc -fpic -DSHARED_MODULE -I/path/to/apache/include -c mod_foo.c
  ld -Bshareable -o mod_foo.so mod_foo.o
  apxs -i -a -n "foo" mod_foo.so
  cp mod_foo.so /path/to/apache/libexec/mod_foo.so
  chmod 755 /path/to/apache/libexec/mod_foo.so
  [activating module `foo' in /path/to/apache/etc/httpd.conf]
  apachectl restart
  /path/to/apache/sbin/apachectl restart: httpd not running, trying to start
  [Tue Mar 31 11:27:55 1998] [debug] mod_so.c(3): loaded module foo_module
  /path/to/apache/sbin/apachectl restart: httpd started
  $ _

You can even use apxs to compile complex modules outside the Apache source tree, like PHP3, because apxs automatically recognized 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.

apachectl(1), apache-perl(8).