Re: [LIP] check instance of a running application

Hi

I think the most safely way is to at the start of your program scan 
the /proc catalog - enter into every process catalog /it can be 
easly recognized, because it is a number/ and read the name of each 
process from file stat - files stat have got the "read" permissions 
for everyone - so you are able to read stat file from every process
.
This is just like works the ps function

It could look like this:

int findprocess(char *programname) //the argument is the name of 
your daemon
    {   
    char myname[256];
    sprintf(myname, "(%s)", programname); //add brackets
    DIR *procdir = opendir("/proc");
    struct dirent *process;
    char fullpath[256] = {}; //it will be used for making full path 
to stat for the scanf function
    int procid = 0; //the process id from stat file
    char procname[32]={}; //the process name from stat file
    FILE* pstat=0;
   
   //here is the start of loop that goes through every entry 
in /proc - of course only on the top level :)
    while(process = readdir(procdir))
    {
     if (atol(process->d_name)) //the program check if the name of 
the entry is a number - if it is - thats the process!
        {
         sprintf(fullpath, "/proc/%s/stat", process->d_name);
         pstat = fopen(fullpath, "r");
         if (pstat != NULL)
            {     
            fscanf(pstat, "%d %s", &procid, procname); //read the 
process id and name - the name is in brackets
            fclose(pstat); //closing the file
            if (!strcasecmp(myname, procname)) //if the (names) are 
the same - process was found - stop loop exit function with 1
                return 1;
            };  
         };
    };
    //if the loop end naturally, that means, that the process 
wasn't found
    return 0;
};

This method has got one minus - it is not resist for changing names 
of the program

Hope To Help
Asia Sledzik

------ Wiadomość oryginalna ------
Od:    Ram <rammohhan2000-/[email protected]>
Data:  2003-12-24 13:45
Temat: [LIP] check instance of a running application

:-> Hi all,
:-> 
:->      In Linux , Thr Coding in c how can i check
:-> whether my application is running or not . i.e i have
:-> written a small c program which will run as a
:-> daemon.When i run the same program  again it should
:-> check whether previous  instance  is running or
:-> not(preferbly with the application name)  , if running
:-> then i have to pass a value to the running application
:-> ..
:-> 
:-> For checking whether app is still running , I tried by
:->  writing the  PID value to a file and later checked
:-> whether it exists or not. is there any other way to do
:-> this....
:-> 
:-> Any solution !.
:-> 
:-> 






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