Пункт 66. Manual Page: apxs
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/apache2.conf]
$ apache2ctl restart
/path/to/apache/sbin/apache2ctl 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/apache2ctl 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.
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 ...
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.
Use this to manually determine settings used to build the
httpd that will load your module. 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 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
apache2.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 apache2.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 apache2.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/apache2.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/apache2.conf]
apache2ctl restart
/path/to/apache/sbin/apache2ctl 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/apache2ctl restart: httpd started
$ _
