examples/PIPS/posixsignals/sigtermSignal/src/sigtermSignal.c

// sigtermSignal.c
//
// Copyright (c) 2010 Nokia Corporation and/or its subsidiary(-ies).
// All rights reserved.
// This component and the accompanying materials are made available
// under the terms of "Eclipse Public License v1.0"
// which accompanies this distribution, and is available
// at the URL "http://www.eclipse.org/legal/epl-v10.html".
//
// Initial Contributors:
// Nokia Corporation - initial contribution.
//
// Contributors:
//
// Description: The source code file for sigtermSignal.
//

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <signal.h>
#include <e32def.h>
#include <time.h>
#include <spawn.h>

FILE *gfp = NULL;
char *testfile = "C:\\testfile.txt";

void PressKey()
    {
    int ch;
    printf("Press 'e'+Enter to exit\n");
    while((ch=getchar())!= 'e')
        {
        if(ch == '\n')
            continue;
        else
            printf("wrong option selected, please try again!!!\n");
        }
    }
void SIGTERM_handler(int signum)
    {
    if(signum == SIGTERM)
        {
        if(gfp != NULL)
            {
            printf("Received the SIGTERM signal from the raiseSignal process\n");
            fclose(gfp);
            remove(testfile);
            gfp = NULL;
            printf("The open file descriptor was closed\n");
            PressKey();
            exit (0);
            }
        }
    }

int main()
    {
    char input[11];   
    int count = 0,num;
    int ch,ret;
    pid_t usrProcsID;
    const int delay = 4;                                    //Time delay of 4 sec provided.
    const int size = 50;                                    //No.of characters allowed in the filename.
    const int index = 3;                                    //No.of elements in the array.
    
    char *usrProcess = "Z:\\sys\\bin\\raisesignal.exe";    //Filename of process used for raising SIGTERM signal.
    char **argv = (char**)malloc(index*sizeof(char*));      //Variable holding values to be passed on to the raiseSignal process. 
    argv[0] = (char*)malloc(size*sizeof(char));
    argv[1] = (char*)malloc(index*sizeof(char));
    argv[2] = NULL;

    
    strcpy(argv[0], "z:\\sys\\bin\\raisesignal.exe");       //argv[0] holding name of the child process.
    sprintf(argv[1],"%d",getpid());                         //argv[1] holding parent pid.

    printf("*****************************************************************************************\n");
    printf("* Welcome to the demonstration of a graceful process termination using a SIGTERM signal *\n");
    printf("*****************************************************************************************\n");
    
    printf("* This example shows how a SIGTERM signal can be used to gracefully terminate a process.\n");
    printf("* The example first creates a process called sigtermSignal, assigns a custom handler\nfor the SIGTERM signal, opens a file and gets names from the user to be written in to it.\n");
    printf("* It then simultaneously spawns a raiseSignal process and starts reading from the file.\n");
    printf("* The raiseSignal process sends a SIGTERM signal to the sigtermSignal process.\n");
    printf("* On receiving the SIGTERM signal, the sigtermSignal process closes all the \nopen file descriptors and prepares to exit.\n");
    
    printf("\nPress the Enter key to continue\n");
    getchar();

    signal(SIGTERM, SIGTERM_handler);
    printf("************ In the sigtermSignal process ************\n");
    printf("Enter the number of names you want to enter (e.g. 8) :\n");
    scanf("%d", &count);
    gfp=fopen(testfile, "w+");   //Opening the file for read and write.
    if(gfp != NULL)
        {
        printf("File open sucessful\n");
        }
    else
        {
        printf("File open failed\n");
        }
    for(num=1; num<=count; num++)
        {
        printf("Name (%d)=", num);
        scanf("%s", input);
        fprintf(gfp, "%s\n", input);
        }
    
    printf("Press the Enter key to spawn the raiseSignal process\n");
    getchar();
    getchar();
    //Spawning raiseSignal process to accept user input.
    ret = posix_spawn(&usrProcsID,usrProcess,NULL,NULL,argv,(char**)NULL);
    if(ret != 0)     
        {         
        printf("\n*** failure posix_spawn ***\n");        
        return EXIT_FAILURE;     
        }
     rewind(gfp);
     printf("Starting to read from the file\n");
     for(num=1; num<=count; num++)
         {
         sleep (delay);       
         printf("Name (%d)=", num);
         while((ch=(fgetc(gfp))) != '\n')
                  {
                  putchar(ch);
                  }
         printf("\n");
         
         }
    if(!fclose(gfp))
        {
        remove(testfile);
        gfp = NULL;
        printf("File closed successfully\n");
        }
    else
        {
        printf("File close failed\n");
        }
  
    PressKey();
    return EXIT_SUCCESS;
    }

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