I wanted to shutdown my linux home media server if there is no running computer on my network. So I wrote this little programs which reads all known ips from DHCP configuration and lease files and send a ping to them. If the ping respond, one PC of my LAN is up…<\/p>\n
To re-start the computer in the morning, I use the BIOS RTC alarm (the thing you have by pressing F1 or ESC on reboot). You could also add a script\/a program on each of your computers to send the magic packet to your home server to wake it by lan (see “wake on lan” on google).<\/p>\n
This script can take any command. But if you want to do shutdown like proposed in the title, you can use :<\/p>\n
[code]sudo .\/autoshut “poweroff” 10.0.0.1[\/code]<\/p>\n
Where 10.0.0.1 is your local IP adress. To compile the program, simply use (after saving the code as “autoshut.c”) : [code]gcc -o autoshut autoshut.c[\/code]<\/p>\n
In my case, I wanted to launch the command only after midnight, so I used cron. Cron will launch that command every 5 minutes from midnight to eight o’clock. So if I stay up late, my server won’t shutdown if my own computer is not down too. That’s the whole purpose.<\/p>\n
The line in my crontab :<\/p>\n
[code]0,10,20,30,40,50 1,2,3,4,5,6,7 * * * root \/home\/tom\/autoshut\/autoshut “poweroff” 10.0.0.1[\/code]<\/p>\n
Why do all that ? Energy consumption…<\/p>\n
[code]#include <stdio.h>
\n#include <stdlib.h>
\n#include <regex.h>
\n#include <string.h><\/p>\n
#define LEASE_FILE “\/var\/lib\/dhcp\/dhcpd.leases”
\n#define DHCP_CONFIG_FILE “\/etc\/dhcp\/dhcpd.conf”<\/p>\n
int in_array(char** ar, char* str) {
\nint i = 0;
\nwhile (ar[i] != NULL) {
\nif (strcmp(ar[i],str) == 0) return 1;
\ni++;
\n}
\nreturn 0;
\n}<\/p>\n
char* extractIP (char* filename, char** list, int* listNum) {
\nFILE *pfile;<\/p>\n
pfile = fopen(filename, “rb”);<\/p>\n
if(pfile == NULL){
\nprintf(“Sorry, can’t open %s\\n”, filename);
\nreturn ‘\\0’;
\n}
\nregex_t reg;
\nint err = regcomp (®, “(10\\\\.[0-1]\\\\.0\\\\.([1-9]|[0-9]{2,3}))”, REG_EXTENDED);
\nif (err != 0)
\n{
\nprintf(“ERREUR\\n”);
\nreturn ‘\\0’;
\n}
\nchar ligne[255];<\/p>\n
while(!feof(pfile)) {
\nfgets(ligne, 254 ,pfile);
\nint match;
\nsize_t nmatch = 0;
\nregmatch_t *pmatch = NULL;<\/p>\n
nmatch = reg.re_nsub;
\npmatch = malloc (sizeof (*pmatch) * nmatch);
\nmatch = regexec (®, ligne, nmatch, pmatch, 0);
\nif (match == 0)
\n{
\nchar *ip = NULL;
\nint start = pmatch->rm_so;
\nint end = pmatch->rm_eo;
\nsize_t size = end – start;<\/p>\n
char* str = malloc(sizeof(char) * 15);
\nstrncpy (str, &ligne[start], size);
\nstr[size] = ‘\\0’;<\/p>\n
if (!in_array(list, str)) {
\nlist[*listNum] = str;
\nprintf(“%s\\n”, str);
\n(*listNum)++;
\n}<\/p>\n
}<\/p>\n
}<\/p>\n
fclose(pfile);
\nregfree(®);
\n}<\/p>\n
int ping(char* address) {<\/p>\n
char cmd[30] = “ping -W 1 -q -c 1 “;
\nstrcat(cmd,address);
\nint ret=system(cmd);
\nprintf(“\\nResultat : %d\\n\\n”,ret);
\nreturn !ret;
\n}
\n\/*
\nTODO : maybe an option?
\nint checkCableStatus(const char* interface) {
\n\/sys\/class\/net\/eth0\/carrier
\n}*\/<\/p>\n
int main(int argc, char** argv) {<\/p>\n
if (argc <= 2) {
\nprintf(“Usage : %s Command Local-IP [Local-IP-2]\\n\\tCommand : a command to execute if ping does not work\\n\\tLocal-IP : Ip to ignore\\n\\tLocal-IP-2 : Optional second ip to ignore”,argv[0]);
\nreturn -1;
\n}
\nint listNum = 0;
\nchar** list = malloc(sizeof(char*) * 255);
\nextractIP(DHCP_CONFIG_FILE, list, &listNum);
\nextractIP(LEASE_FILE, list, &listNum);
\nint i = 0;
\nwhile (list[i] != NULL) {
\nif (strcmp(list[i],argv[2])!=0 && (argc==3 ||strcmp(list[i],argv[3])!=0)) {
\nif (ping (list[i])) {
\nprintf(“%s responded. Command aborted !\\n”,list[i]);
\nreturn EXIT_SUCCESS;
\n}
\n}
\ni++;
\n}
\nsystem(argv[1]);
\nreturn EXIT_SUCCESS;
\n}[\/code]<\/p>\n","protected":false},"excerpt":{"rendered":"
I wanted to shutdown my linux home media server if there is no running computer on my network. So I wrote this little programs which reads all known ips from DHCP configuration and lease files and send a ping to them. If the ping respond, one PC of my LAN is up… To re-start the … <\/p>\n