apxs - Online in the Cloud

PROGRAM:

NAME

apxs - APache eXtenSion tool

SYNOPSIS

apxs -g [ -S name=value ] -n modname

apxs -q [ -v ] [ -S name=value ] query ...

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

apxs -i [ -S name=value ] [ -n modname ] [ -a ] [ -A ] dso-file ...

apxs -e [ -S name=value ] [ -n modname ] [ -a ] [ -A ] dso-file ...

SUMMARY

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 httpd 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

$ httpd -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/modules/mod_foo.so
chmod 755 /path/to/apache/modules/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(303): 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
used the C source files for compilation while just using 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 dynamically loaded shared
object. For instance with GCC you always just have to use -fpic. For other C compilers
consult its manual page or at watch for the flags apxs uses to compile the object files.

For more details about DSO support in Apache read the documentation of mod_so or perhaps
even read the src/modules/standard/mod_so.c source file.

OPTIONS

Common Options
-n modname
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 variables and environment settings used to build httpd. When
invoked without query parameters, it prints all known variables and their values.
The optional -v parameter formats the list output. .PP Use this to manually
determine settings used to build the httpd that will load your module. For instance
use INC=-I`apxs -q INCLUDEDIR` .PP inside your own Makefiles if you need manual
access to Apache's C header files.

Configuration Options
-S name=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 build 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 dynamically shared
object 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 dynamically shared object. If not
specified and the name cannot be guessed from the files list, the fallback name
mod_unknown.so is used.

-D name=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 libtool --mode=compile
command. Use this to add local compiler-specific options.

-Wl,linker-flags
This option passes linker-flags as additional flags to the libtool --mode=link
command. Use this to add local linker-specific options.

-p This option causes apxs to link against the apr/apr-util libraries. This is useful
when compiling helper programs that use the apr/apr-util libraries.

DSO Installation and Configuration Options
-i This indicates the installation operation and installs one or more dynamically
shared objects into the server's modules directory.

-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.

-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 httpd.conf configuration file
without attempting to install the module.

EXAMPLES

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
shared object suitable for loading into the Apache server under runtime via the following
command:

$ apxs -c mod_foo.c
/path/to/libtool --mode=compile gcc ... -c mod_foo.c
/path/to/libtool --mode=link gcc ... -o mod_foo.la mod_foo.slo
$ _

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

$ apxs -i -a mod_foo.la
/path/to/instdso.sh mod_foo.la /path/to/apache/modules
/path/to/libtool --mode=install cp mod_foo.la /path/to/apache/modules
...
chmod 755 /path/to/apache/modules/mod_foo.so
[activating module `foo' in /path/to/apache/conf/httpd.conf]
$ _

This way a line named

LoadModule foo_module modules/mod_foo.so

is added to the configuration file if still not present. If you want to have this disabled
per default 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/modules.mk
Creating [FILE] foo/mod_foo.c
Creating [FILE] foo/.deps
$ _

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

$ cd foo
$ make all reload
apxs -c mod_foo.c
/path/to/libtool --mode=compile gcc ... -c mod_foo.c
/path/to/libtool --mode=link gcc ... -o mod_foo.la mod_foo.slo
apxs -i -a -n "foo" mod_foo.la
/path/to/instdso.sh mod_foo.la /path/to/apache/modules
/path/to/libtool --mode=install cp mod_foo.la /path/to/apache/modules
...
chmod 755 /path/to/apache/modules/mod_foo.so
[activating module `foo' in /path/to/apache/conf/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(303): loaded module foo_module
/path/to/apache/sbin/apachectl restart: httpd started
$ _

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