https://github.com/jirihnidek/daemon

Simple example of daemon for Linux
https://github.com/jirihnidek/daemon

c example linux systemd sysvinit unix-daemon

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Simple example of daemon for Linux

• Host: GitHub
• URL: https://github.com/jirihnidek/daemon
• Owner: jirihnidek
• License: gpl-2.0
• Created: 2015-02-27T09:58:28.000Z (over 9 years ago)
• Default Branch: master
• Last Pushed: 2024-10-22T10:14:38.000Z (25 days ago)
• Last Synced: 2024-10-23T13:59:11.030Z (24 days ago)
• Topics: c, example, linux, systemd, sysvinit, unix-daemon
• Language: C
• Homepage:
• Size: 33.2 KB
• Stars: 363
• Watchers: 21
• Forks: 112
• Open Issues: 2
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
# Example of Linux Daemon

This repository contains simple example of daemon for Linux OS.

This repository also contains examples of starting scripts.

When you want to create super simple daemon, then it is very easy.

You can write something like this in C and call it `daemon.c`:

```c

/* Compile this with gcc -o daemon daemon.c */

#include 

int main(void)

{

    while(1) {

        /* TODO: do something usefull here ;-) */

        sleep(1);

    }

}

```

and write some super simple systemd service file called `simple-daemon.service`:

    [Unit]

    Description=Super simple daemon

    [Service]

    Type=simple

    ExecStart=/usr/bin/daemon

    [Install]

    WantedBy=multi-user.target

and then you can run it as UNIX daemon, but such daemon do not have some

nice features like reloadin configure files, loging, etc. This repository

and sources can help you to understand how UNIX daemons works. 

## Requirements

To build example of the daemon you have to have following tools

* CMake

* GCC/CLang

## Build

To build example of daemon you have to type following commands:

    git clone https://github.com/jirihnidek/daemon.git

    cd daemon

    mkdir build

    cd build

    cmake -DCMAKE_INSTALL_PREFIX=/usr ../

    make

    sudo make install

## Usage

You can test running daemon from command line:

    ./bin/daemon

But running the app in this way is not running running daemon. Let

have a look at command line parameters and arguments

    Usage: ./bin/daemon [OPTIONS]

     Options:

      -h --help                 Print this help

      -c --conf_file filename   Read configuration from the file

      -t --test_conf filename   Test configuration file

      -l --log_file  filename   Write logs to the file

      -d --daemon               Daemonize this application

      -p --pid_file  filename   PID file used by daemonized app

When you will run `./bin/daemon` with parameter `--daemon` or `-d`, then

it will become real UNIX daemon. But this is not the way, how UNIX daemons

are started nowdays. Some init scripts or service files are used for

this purpose.

When you use Linux distribution using systemd, then you can try start daemon using

    systemctl start simple-daemon

    systemctl status simple-daemon

    systemctl reload simple-daemon

    systemctl stop simple-daemon

> Note: The unit files `simple-daemon.service` and `forking-daemon.service` 

are copied to the directory `/usr/lib/systemd/system` during installation using

`make install` command.

When you use RedHat 4/5/6 or CentOS, then you can try to use init script:

    cp daemon.init /etc/rc.d/init.d/daemond

Then it should be possible to control daemon using:

    service daemon start

    service daemon status

    service daemon reload

    service daemon stop