making program daemon

yahoosam · 07-31-2012, 12:58 AM

how can I make my program a daemon..
Actually i have a program whose binary "./Update" i want to execute as daemon..
Any idea!
please post in here with simple coading mechanism.

evo2 · 07-31-2012, 01:22 AM

Hi,

basically you need to detach from the console where the program is launched. This usually means forking twice and redirecting stdin/stdout/stderr, changing the current directory to /, set umask to 0... I've seen ready made tools/recipes for doing this in a number of languages including C, python and even shell script! What language is your code written in?

Evo2.

yahoosam · 07-31-2012, 02:43 AM

it's in C...
can you provide me one of the sample in c.

evo2 · 07-31-2012, 03:15 AM

Hi,

my search engine returned the following tutorial:

http://www.systhread.net/texts/200506cdaemon1.php

Part 2 of the tutorial shows what to do with stdin/stdout/stderr.

Evo2.

okcomputer44 · 07-31-2012, 04:02 AM

Hi,

Quote:

nohup COMMAND &

The COMMAND will be sent to the background.
If you want to stop it, you have to use

Quote:

kill PROCESSID

Man page about nohup:

Quote:

NAME
nohup - run a command immune to hangups, with output to a non-tty

SYNOPSIS
nohup COMMAND [ARG]...
nohup OPTION

DESCRIPTION
Run COMMAND, ignoring hangup signals.

--help display this help and exit

--version
output version information and exit

If standard input is a terminal, redirect it from /dev/null. If standard output is a
terminal, append output to ‘nohup.out’ if possible, ‘$HOME/nohup.out’ otherwise. If
standard error is a terminal, redirect it to standard output. To save output to FILE,
use ‘nohup COMMAND > FILE’.

NOTE: your shell may have its own version of nohup, which usually supersedes the version
described here. Please refer to your shell’s documentation for details about the options
it supports.

I hope it helps.

Laz

NevemTeve · 07-31-2012, 04:34 AM

Actual (if minimal) example script:

Code:

#!/bin/sh

trap '' SIGHUP

cd /home/projects/hol
exec >>log/f_giro.log 2>&1

bin/f_giro &

echo "$!">/var/run/f_giro.pid

yahoosam · 07-31-2012, 08:08 AM

The link was really Awesome...
within those two pages it described all with good understanding..
Thanks a lot

evo2 · 07-31-2012, 07:05 PM

Hi,

since others have made suggestions on how to do this with a shell script wrapper instead of actually coding your program as a daemon, I thought it worthwhile posting the shell script wrapper I have used in the past for daemonizing programs. This script also includes start/stop/restart mechanisms.
Credit for the first three functions goes to http://blog.n01se.net/?p=145

Code:

#!/bin/bash
redirect-std() {
    [[ -t 0 ]] && exec </dev/null
    [[ -t 1 ]] && exec >/dev/null
    [[ -t 2 ]] && exec 2>/dev/null
}
 
# close all non-std* fds
close-fds() {
    eval exec {3..255}\>\&-
}
 
# full daemonization of external command with setsid
daemonize() {
    (                   # 1. fork
        redirect-std    # 2.1. redirect stdin/stdout/stderr before setsid
        cd /            # 3. ensure cwd isn't a mounted fs
        # umask 0       # 4. umask (leave this to caller)
        close-fds       # 5. close unneeded fds
        exec setsid "$@"
    ) &
}
###########################################################################

DAEMON="someprogram"
EXE="/path/to/somwhere/${DAEMON}"
KILL="/bin/kill"
if [ ! -x $EXE ] ; then
    echo "$EXE not found"
    exit 1
fi

SELF="$(basename $0)"
USER="$(whoami)"
LOCKFILE="/tmp/${DAEMON}-${USER}.lock"

dostart() {
    echo -n "Starting $DAEMON ... " 2>&1

    if [ -e ${LOCKFILE} ] ; then
        echo "Failed."
        echo "Lockfile ${LOCKFILE} exists." 2>&1
        echo "Appears ${DAEMON} already running. To restart try:" 2>&1
        echo "${SELF} restart" 2>&1
        echo "Failing that, manually kill $DAEMON and remove ${LOCKFILE}" 2>&1
        return
    fi

    daemonize ${EXE}
    PID="$!"
    echo ${PID} > ${LOCKFILE}
    echo "Ok." 2>&1
}

dostop() {
    echo -n "Stopping ${DAEMON} ... " 2>&1
    if [ ! -f ${LOCKFILE} ] ; then
        echo "${DAEMON} appears not to be running." 2>&1
        return
    fi
    PID=$(cat ${LOCKFILE})
    NAME_OF_PID=$(ps --pid ${PID} -o comm h)
    if [ "x${NAME_OF_PID}" != "x${DAEMON}" ] ; then
        echo "" 2>&1
        echo "Can't find $DAEMON (pid $PID)." 2>&1
        echo "Removing lockfile: ${LOCKFILE}" 2>&1
        rm -f ${LOCKFILE}
        return
    fi

    # Kill the daemon
    echo -n "(kill $PID) ... " 2>&1
    $KILL $PID
    if [ "$?" != "0" ] ; then
        echo "" 2>&1
        echo "Failed to kill $DAEMON (pid $PID)" 2>&1
    else
        echo "Ok." 2>&1
        echo -n "Removing lock file ... " 2>&1
        rm -f ${LOCKFILE}
        echo "Ok." 2>&1
    fi
}

dorestart() {
    dostop
    dostart
}

case "$1" in
    start)
        dostart
        ;;
    stop)
        dostop
        ;;
    restart|reload|force-reload)
        dorestart
        ;;
    *)
        echo "Usage: $SELF {start|stop|reload|force-reload|restart}" 2>&1
        exit 1
esac

You just need to edit

Code:

DAEMON="someprogram"
EXE="/path/to/somwhere/${DAEMON}"

as desired.

There are places where it could us a bit of a cleanup (eg the dostop() function could probably do with a rewrite using pkill), but it should work as is.

HTH,

EVo2.