The Special System Classes

The system provides four special classes. They are:

• The sed class

  Provides a method for using sed instructions to edit files upon package installation and removal.

• The awk class

  Provides a method for using awk instructions to edit files upon package installation and removal.

• The build class

  Provides a method to dynamically construct or modify a file using Bourne shell commands.

• The preserve class

  Provides a method to preserve files that should not be overwritten by future package installations.

If there are several files in a package that require special processing that can be fully defined through sed, awk, or sh commands, installation will be faster by using the system classes rather than multiple classes and their corresponding class action scripts.

The sed Class Script

The sed class provides a method to modify an existing object on the target system. The sed class action script executes automatically at installation if a file belonging to class sed exists. The name of the sed class action script should be the same as the name of the file on which the instructions will be executed.

A sed class action script delivers sed instructions in the format shown in the figure below.

Figure 3–1 Format of a sed Class Action Script

# comment, which may appear on any line in the file
 
!install
# sed(1) instructions which will be invoked during
# installation of the object
 
[address [,address]] function [arguments]
 
  . . .
 
!remove
 
# sed(1) instructions to be invoked during the removal process
 
[address [,address]] function [arguments]

Two commands indicate when instructions should be executed. The sed instructions that follow the !install command are executed during package installation and those that follow the !remove command are executed during package removal. It does not matter which order these commands are used in the file.

For more information on sed instructions, see sed(1). For examples of sed class action scripts, see Chapter 5, Package Creation Case Studies.

The awk Class Script

The awk class provides a method to modify an existing object on the target system. Modifications are delivered as awk instructions in an awk class action script.

The awk class action script is executed automatically at installation if a file belonging to class awk exists. Such a file contains instructions for the awk class script in the format shown in the figure below.

Figure 3–2 Format of an awk Class Action Script

# comment, which may appear on any line in the file
 
!install
 
# awk(1) program to install changes
 
 . . . (awk program)
 
!remove
 
# awk1(1) program to remove changes
 
 . . . (awk program)

Two commands indicate when instructions should be executed. The awk instructions that follow the !install command are executed during package installation, and those that follow the !remove command are executed during package removal. It does not matter in which order these commands are used in the file.

The name of the awk class action script should be the same as the name of the file on which the instructions will be executed.

The file to be modified is used as input to awk and the output of the script ultimately replaces the original object. Environment variables may not be passed to the awk command with this syntax.

For more information on awk instructions, see awk(1).

The build Class Script

The build class creates or modifies a package object file by executing Bourne shell instructions. These instructions are delivered as the package object, which runs automatically at installation if it belongs to the build class.

The name of the build class action script should be the same as the name of the file on which the instructions will be executed, and must be executable by the sh command. The script's output becomes the new version of the file as it is built or modified. If the script produces no output, the file will not be created or modified. Therefore, the script can modify or create the file itself.

For example, if a package delivers a default file, /etc/randomtable, and if the file does not already exist on the target system, the prototype file entry might be:

e build /etc/randomtable ? ? ?

and the package object, /etc/randomtable, might look like this:

!install
# randomtable builder
if [ -f $PKG_INSTALL_ROOT/etc/randomtable ]; then
		echo "/etc/randomtable is already in place.";
	    else
		echo "# /etc/randomtable" > $PKG_INSTALL_ROOT/etc/randomtable
		echo "1121554	# first random number" >> $PKG_INSTALL_ROOT/etc/randomtable
fi
 
!remove
# randomtable deconstructor
if [ -f $PKG_INSTALL_ROOT/etc/randomtable ]; then
		# the file can be removed if it's unchanged
		if [ egrep "first random number" $PKG_INSTALL_ROOT/etc/randomtable ]; then
			rm $PKG_INSTALL_ROOT/etc/randomtable;
		fi
fi
 

See Chapter 5, Package Creation Case Studies for another example using the build class.

The preserve Class Script

The preserve class preserves a package object file by determining whether or not an existing file should be overwritten when the package is installed. Two possible scenarios when using a preserve class script are:

• If the file to be installed does not already exist in the target directory, the file will be installed normally.

• If the file to be installed exists in the target directory, a message describing the file exists is displayed, and the file is not installed.

Both scenario outcomes are considered successful by the preserve script. A failure occurs only, when in the second scenario, the file is unable to be copied to the target directory.

Starting with the Solaris 7 release, the i.preserve script and a copy of this script, i.CONFIG.prsv, can be found in the /usr/sadm/install/scripts directory with the other class action scripts.

Modify the script to include the filename or filenames you would like to preserve.