lfs-book/chapter07/functions.xml

<sect1 id="ch07-functions">
<title>Creating the functions script</title>

<para>
Create the <filename>/etc/init.d/functions</filename> script by running
the following command:
</para>

<para>
<screen>
<userinput>cat &gt; functions &lt;&lt; "EOF"</userinput>
#!/bin/sh
# Begin /etc/init.d/functions

#
# Set a few variables that influence the text that's printed on the
# screen. The SET_COL variable starts the text in the column number 
# decided by the COL and WCOL section (as defined by the COL 
# variable). NORMAL prints text in normal mode.
# SUCCESS prints text in a green colour and FAILURE prints text in a red
# colour
#

# If COLUMNS hasn't been set yet (bash sets it but not when called as
# sh), do it ourself

	if [ -z "$COLUMNS" ]
    	then
        	# Get the console device if we don't have it already
		# This is ok by the FHS as there is a fallback if
		# /usr/bin/tty isn't available, for example at bootup.
        	test -x /usr/bin/tty &amp;&amp; CONSOLE=`/usr/bin/tty`
        	test -z "$CONSOLE" &amp;&amp; CONSOLE=/dev/console

    		# Get the console size (rows columns)
        	SIZE=$(stty size &lt; $CONSOLE)
 
    		# Strip off the rows leaving the columns
      		COLUMNS=${SIZE#*\ }
	fi
 
COL=$[$COLUMNS - 10]
WCOL=$[$COLUMNS - 30]
SET_COL="echo -en \\033[${COL}G"
SET_WCOL="echo -en \\033[${WCOL}G"
NORMAL="echo -en \\033[0;39m"
SUCCESS="echo -en \\033[1;32m"
WARNING="echo -en \\033[1;33m"
FAILURE="echo -en \\033[1;31m"

#
# The evaluate_retval function evaluates the return value of the process
# that was run just before this function was called. If the return value
# was 0, indicating success, the print_status function is called with
# the 'success' parameter. Otherwise the print_status function is called
# with the failure parameter.
#

evaluate_retval()
{
        if [ $? = 0 ]
        then
                print_status success
        else
                print_status failure
        fi
}

#
# The print_status prints [  OK  ] or [FAILED] to the screen. OK appears
# in the colour defined by the SUCCESS variable and FAILED appears in
# the colour defined by the FAILURE variable. Both are printed starting
# in the column defined by the COL variable.
#

print_status()
{

#
# If no parameters are given to the print_status function, print usage
# information.
#

        if [ $# = 0 ]
        then
                echo "Usage: print_status {success|failure}"
                return 1
        fi

        case "$1" in
                success)
                        $SET_COL
                        echo -n "[  "
                        $SUCCESS
                        echo -n "OK"
                        $NORMAL
                        echo "  ]"
                        ;;
                warning)
                        $SET_COL
                        echo -n "[ "
                        $WARNING
                        echo -n "ATTN"
                        $NORMAL
                        echo " ]"
                        ;;
                failure)
                        $SET_COL
                        echo -n "["
                        $FAILURE
                        echo -n "FAILED"
                        $NORMAL
                        echo "]"
                        ;;
        esac

}

#
# The loadproc function starts a process (often a daemon) with
# proper error checking
#

loadproc()
{

#
# If no parameters are given to the print_status function, print usage
# information.
#

        if [ $# = 0 ]
        then
                echo "Usage: loadproc {program}"
                exit 1
        fi
#
# Find the basename of the first parameter (the daemon's name without
# the path
# that was provided so /usr/sbin/syslogd becomes plain 'syslogd' after
# basename ran)
#

        base=$(/usr/bin/basename $1)
#
# the pidlist variable will contains the output of the pidof command.
# pidof will try to find the PID's that belong to a certain string;
# $base in this case
#

        pidlist=$(/bin/pidof -o $$ -o $PPID -o %PPID -x $base)

        pid=""

        for apid in $pidlist
        do
                if [ -d /proc/$apid ]
                then
                        pid="$pid $apid"
                fi
        done
#
# If the $pid variable contains anything (from the previous for loop) it
# means the daemon is already running
#

        if [ ! -n "$pid" ]
        then
#
# Empty $pid variable means it's not running, so we run "$@" (all
# parameters giving to this function from the script) and then check the
# return value
#

                "$@"
                evaluate_retval
        else
#
# The variable $pid was not empty, meaning it was already running. We'll
# print [ ATTN ] now
#

                $SET_WCOL
                echo -n "Already running"
                print_status warning
        fi

}

#
# The killproc function kills a process with proper error checking
#

killproc()
{

#
# If no parameters are given to the print_status function, print usage
# information.
#

        if [ $# = 0 ]
        then
                echo "Usage: killproc {program} [signal]"
                exit 1
        fi

#
# Find the basename of the first parameter (the daemon's name without
# the path
# that was provided so /usr/sbin/syslogd becomes plain 'syslogd' after
# basename ran)
#

        base=$(/usr/bin/basename $1)

#
# Check if we gave a signal to kill the process with (like -HUP, -TERM,
# -KILL, etc) to this function (the second parameter). If no second
# parameter was provided set the nolevel variable. Else set the
# killlevel variable to the value of $2 (the second parameter)
#

        if [ "$2" != "" ]
        then
                killlevel=-$2
        else
                nolevel=1
        fi

#
# the pidlist variable will contains the output of the pidof command.
# pidof will try to find the PID's that belong to a certain string;
# $base in this case
#

        pidlist=$(/bin/pidof -o $$ -o $PPID -o %PPID -x $base)

        pid=""

        for apid in $pidlist
        do
                if [ -d /proc/$apid ]
                then
                        pid="$pid $apid"
                fi
        done

#
# If $pid contains something from the previous for loop it means one or
# more PID's were found that belongs to the processes to be killed
#

        if [ -n "$pid" ]
        then

#
# If no kill level was specified we'll try -TERM first and then sleep
# for 2 seconds to allow the kill to be completed
#

                if [ "$nolevel" = 1 ]
                then
                        /bin/kill -TERM $pid

#
# If after -TERM the PID still exists we'll wait 2 seconds before
# trying to kill it with -KILL. If the PID still exist after that, wait
# two more seconds. If the PIDs still exist by then it's safe to assume
# that we cannot kill these PIDs.
#

                        if /bin/ps h $pid &gt;/dev/null 2&gt;&amp;1
                        then
                                /usr/bin/sleep 2
                                if /bin/ps h $pid &gt; /dev/null 2&gt;&amp;1
                                then
                                        /bin/kill -KILL $pid
                                        if /bin/ps h $pid &gt; /dev/null 2&gt;&amp;1
                                        then
                                                /usr/bin/sleep 2
                                        fi
                                fi
                        fi
                        /bin/ps h $pid &gt;/dev/null 2&gt;&amp;1
                        if [ $? = 0 ]
                        then
#
# If after the -KILL it still exists it can't be killed for some reason
# and we'll print [FAILED]
#

                                print_status failure
                        else

#
# It was killed, remove possible stale PID file in /var/run and 
# print [  OK  ]
#

                                /bin/rm -f /var/run/$base.pid
                                print_status success
                        fi
                else

#
# A kill level was provided. Kill with the provided kill level and wait
# for 2 seconds to allow the kill to be completed
#

                        /bin/kill $killlevel $pid
                        if /bin/ps h $pid &gt; /dev/null 2&gt;&amp;1
                        then
                                /usr/bin/sleep 2
                        fi
                        /bin/ps h $pid &gt;/dev/null 2&gt;&amp;1
                        if [ $? = 0 ]
                        then

#
# If ps' return value is 0 it means it ran ok which indicates that the
# PID still exists. This means the process wasn't killed properly with
# the signal provided. Print [FAILED]
#

                                print_status failure
                        else

#
# If the return value was 1 or higher it means the PID didn't exist
# anymore which means it was killed successfully. Remove possible stale
# PID file and print [  OK  ]
#

                                /bin/rm -f /var/run/$base.pid
                                print_status success
                        fi
                fi
        else

#
# The PID didn't exist so we can't attempt to kill it. Print [ ATTN ]
#

                $SET_WCOL
                echo -n "Not running"
                print_status warning
        fi
}

#
# The reloadproc functions sends a signal to a daemon telling it to
# reload it's configuration file. This is almost identical to the
# killproc function with the exception that it won't try to kill it with
# a -KILL signal (aka -9)
#

reloadproc()
{

#
# If no parameters are given to the print_status function, print usage
# information.
#

        if [ $# = 0 ]
        then
                echo "Usage: reloadproc {program} [signal]"
                exit 1
        fi

#
# Find the basename of the first parameter (the daemon's name without
# the path that was provided so /usr/sbin/syslogd becomes plain 'syslogd' 
# after basename ran)
#

        base=$(/usr/bin/basename $1)

#
# Check if we gave a signal to send to the process (like -HUP)
# to this function (the second parameter). If no second
# parameter was provided set the nolevel variable. Else set the
# killlevel variable to the value of $2 (the second parameter)
#

        if [ -n "$2" ]
        then
                killlevel=-$2
        else
                nolevel=1
        fi

#
# the pidlist variable will contains the output of the pidof command.
# pidof will try to find the PID's that belong to a certain string;
# $base in this case
#

        pidlist=$(/bin/pidof -o $$ -o $PPID -o %PPID -x $base)

        pid=""

        for apid in $pidlist
        do
                if [ -d /proc/$apid ]
                then
                        pid="$pid $apid"
                fi
        done

#
# If $pid contains something from the previous for loop it means one or
# more PID's were found that belongs to the processes to be reloaded
#

        if [ -n "$pid" ]
        then

#
# If nolevel was set we will use the default reload signal SIGHUP.
#

                if [ "$nolevel" = 1 ]
                then
                        /bin/kill -SIGHUP $pid
                        evaluate_retval
                else

#
# Else we will use the provided signal
#

                        /bin/kill $killlevel $pid
                        evaluate_retval
                fi
        else

#
# If $pid is empty no PID's have been found that belong to the process.
# Print [ ATTN ]
#

                $SET_WCOL
                echo -n "Not running"
                print_status warning
        fi
}

#
# The statusproc function will try to find out if a process is running
# or not
#

statusproc()
{

#
# If no parameters are given to the print_status function, print usage
# information.
#

        if [ $# = 0 ]
        then
                echo "Usage: status {program}"
                return 1
        fi

#
# $pid will contain a list of PID's that belong to a process
#

        pid=$(/bin/pidof -o $$ -o $PPID -o %PPID -x $1)
        if [ -n "$pid" ]
        then

#
# If $pid contains something, the process is running, print the contents
# of the $pid variable
#

                echo "$1 running with Process ID $pid"
                return 0
        fi

#
# If $pid doesn't contain it check if a PID file exists and inform the
# user about this stale file.
#

        if [ -f /var/run/$1.pid ]
        then
                pid=$(/usr/bin/head -1 /var/run/$1.pid)
                if [ -n "$pid" ]
                then
                        echo "$1 not running but /var/run/$1.pid exists"
                        return 1
                fi
        else
                echo "$1 is not running"
        fi

}

# End /etc/init.d/functions
<userinput>EOF</userinput>
</screen>
</para>

</sect1>