Port Windows IPC Apps to Linux, Part 1: Processes and Threads

//Sample Application that explain process concepts



//Parameters Declaration/Definition



int TimetoWait;

STARTUPINFO si;

PROCESS_INFORMATION pi;

LPTSTR lpszCurrValue,LPTSTR lpszVariable;

TCHAR tchBuf[BUFSIZE];

BOOL fSuccess;



if(argc > 2)

{

    printf("InvalidArgument");

    ExitProcess(1); //Failure

}



//Get and display an  environment variable PATH

lpszCurrValue = ((GetEnvironmentVariable("PATH",tchBuf, BUFSIZE) > 0) ? tchBuf : NULL);

lpszVariable = lpszCurrValue;



//Display the environment variable

while (*lpszVariable)

    putchar(*lpszVariable++);

putchar('\n');



//Initialise si and pi

ZeroMemory( &si, sizeof(si) );

si.cb = sizeof(si);

ZeroMemory( &pi, sizeof(pi) );



//Create a childProcess

if( !CreateProcess( NULL,             // No module name (use command line).

                    "SomeProcess",    // Command line.

                    NULL,             // Process handle not inheritable.

                    NULL,             // Thread handle not inheritable.

                    FALSE,            // Set handle inheritance to FALSE.

                    0,                // No creation flags.

                    NULL,             // Use parent's environment block.

                    NULL,             // Use parent's starting directory.

                    &si,              // Pointer to STARTUPINFO structure.

                    &pi )             // Pointer to PROCESS_INFORMATION structure.

                        )

{

    printf( "CreateProcess failed." );

}



// Wait until child process exits.

if(argc == 2)

{

    TIMEOUT = atoi(argv[1]);

    ret = WaitForSingleObject( pi.hProcess, TIMEOUT );

    if(ret == WAIT_TIMEOUT)

    {

        TerminateProcess(pi.hProcess);

    }

}

else

{

    WaitForSingleObject( pi.hProcess, INFINITE );

    ...

}

    ExitProcess(0); //Success

#include <stdlib.h>



int main(int argc,char *argv[])

{

    //Parameters Declaration/Definition





    char PathName[255];

    char *Argptr[20];

    int rc;

    char *EnvValue,*lpszVariable;



    if(argc > 1)

    {

        printf(" Wrong parameters !!");

        exit(EXIT_FAILURE);

    }

    //Get and display an  environment variable PATH

    EnvValue = getenv("PATH");

    if(EnvValue == NULL)

    {

        printf("Invalid environment variable passed as param !!");

    }else

    {

        lpszVariable = EnvValue;

        while (*lpszVariable)

            putchar(*lpszVariable++);

        putchar('\n');

    }

    rc = fork(); //variable rc's value on success would be process ID in the parent

                 //process, and 0 in the child's thread of execution.

    switch(rc)

    {

        case -1:

            printf("Fork() function failed !!");

            ret = -1;

            break;

        case 0:

            printf("Child process...");

            setpgid(0,0);  //Change the parent grp ID to 0





        ret = execv(PathName,Argptr); // there are other flavours of exec available,

                                      // u can use any of them based on the arguments.

        if(ret == -1)

        {

            kill(getpid(),0);

        }

        break;

         default:

             // infinitely waits for child process to die

             Waitpid(rc,&status,WNOHANG);

             //Note RC will have PID returned since this is parent process.



             break;

    }

    exit(EXIT_SUCCESS);

}