writing-scripts.md

Writing Scripts

Contents

The Init RC file
Configuration file
Post-Install scripts

#The Init RC file

The Init RC file is the main serivce script. This file should be named initrc in your project source folder (i.e. src/project/initrc).

The idea is the simpliest way to write a service script using a bourne shell syntax, and basically we use only the start and stop functions, leaving restart calling stop following start. Here is an little example

name="myservice"

some_func_to_check_config() { ... }

start() {
    some_func_to_check_config
    cbegin "starting ${name}"
    myservice --start # The service
    cend $?           # The return status from previous command
}

stop() {
    cbegin "stopping ${name}"
    myservice --stop # The service
    cend $?          # The return status from previous command
}

In the script can notice, the cend and cbegin functions, this functions are built-in in CrossRC to manipulate output and service info. This functinos later will be translated to the native functions of the target plataform initrc systen.

If you want to add more arguments you need to set $extra_args variable and create a functino with the name of the arg.

extra_args="status checkconf"

status() { ... }
checkconf() { ... }

start() {
...

Function	args	Description
cbegin	msg	The service related message (Starting service)
cminfo	msg...	Prints a information message
cwarn	msg...	Prints a warning message
cerror	msg...	Prints a error message
cend	status	If $status is 0 print OK/done and if $status is 1 print error/fail and return $status

This functinos are based on gentoo init system

#Config File

The config file almost always is just a few variables to conf the service, and should be named config in your project source folder (i.e. src/project/config).

The config file will be sourced at the top of the script, and his path or name depends on the platforms configuration.

#Post-Install scripts

To empower the install you can use post-install scripts here are some information of how to create one and some examples to give some ideas.

You can create post-install files per-platform i.e

 src/project/include/linux.gentoo/post-install.sh

And just for all

 src/project/include/post-install.sh

The two types of post-install executes separetly, first the platform post-install and the include post-install after.

You can use any variable from de crossrc environment inside the scripts

Examples of post install commands

• Create a service-only user

    useradd -r -d /nonexistant -U -s /bin/true user
  

• Create a log folder in /var/log

     install -d -g use -o group -m 755 /var/log/fstream