TB10.1 Example Applications: examples/PIPS/posixsignals/asyncSignal/src/sigusr1.c Source File

00001 // sigusr1.c
+00002 //
+00003 // Copyright (c) 2010 Nokia Corporation and/or its subsidiary(-ies).
+00004 // All rights reserved.
+00005 // This component and the accompanying materials are made available
+00006 // under the terms of "Eclipse Public License v1.0"
+00007 // which accompanies this distribution, and is available
+00008 // at the URL "http://www.eclipse.org/legal/epl-v10.html".
+00009 //
+00010 // Initial Contributors:
+00011 // Nokia Corporation - initial contribution.
+00012 //
+00013 // Contributors:
+00014 //
+00015 // Description:This example demonstrates asynchronous signal handling.
+00016 //
+00017 
+00018 
+00019 #include <stdio.h>
+00020 #include <stdlib.h>
+00021 #include <signal.h> //The header for signal functionality.
+00022 #include <unistd.h> //The header used for getpid().
+00023 #include <e32def.h>
+00024 #include <spawn.h>
+00025 
+00026 int gch;            // The variable holding a character value, input by the user.
+00027 FILE *gfp = NULL;   // The file descriptor variable holding pointer to asyncFile.txt.
+00028 pid_t chldProcsID;  // The variable for holding the sigusr2 PID.
+00029 int gVal = TRUE;    // Variable used as a boolean value.
+00033 void SIGUSR1_handler(int signum)
+00034     {
+00035     int ret;
+00036     const int delay1 = 1;  //Time delay of 1 sec.
+00037     if (signum == SIGUSR1)
+00038         {
+00039         gVal = FALSE;
+00040         printf("\nReceived the SIGUSR1 signal from the sigusr2 process\n");
+00041         printf("Starting to read from the file\n");
+00042         while((gch = fgetc(gfp))!='\n')
+00043             {
+00044             putchar(gch);  //Writing to stdout.
+00045             }
+00046         printf("\n");  
+00047         sleep (delay1);     
+00048         
+00049         //Sending SIGUSR2 signal to sigusr2 process once the file content is written to the console.
+00050         printf("Reading from the file now completed, sending SIGUSR2 to the sigusr2 process\n");
+00051         
+00052         //Raising SIGUSR2 signal using kill command.
+00053         ret = kill(chldProcsID,SIGUSR2);
+00054         if(ret)
+00055             {
+00056             printf("kill() failed to send signal, errno=%d\n",errno);
+00057             }
+00058         }
+00059     }
+00060 
+00074 int main()
+00075     {
+00076     int ret;
+00077     const int delay = 1;                                        //Delay of 1 sec provided to wait for signal.
+00078     const int size = 50;                                        //No.of characters allowed in the filename.
+00079     const int index = 3;                                        //No.of elements in the array.
+00080     
+00081     char *filename = "C:\\asyncFile.txt" ;                      //Filename of the file that holds names input by the user.
+00082     char *childProcess = "Z:\\sys\\bin\\sigusr2.exe";           //Filename of sigusr2 process.
+00083     char **argv = (char**)malloc(index*sizeof(char*));          //Variable holding values to be passed to the sigusr2 process.
+00084     argv[0] = (char*)malloc(size*sizeof(char));
+00085     argv[1] = (char*)malloc(index*sizeof(char));
+00086     argv[2] = NULL;
+00087 
+00088     
+00089     strcpy(argv[0], "z:\\sys\\bin\\sigusr2.exe");               //argv[0] holding name of the sigusr2 process.
+00090     sprintf(argv[1],"%d",getpid());                             //argv[1] holding PID of sigusr1 process.
+00091     
+00092     //Setup the custom handler for SIGUSR1.
+00093     signal(SIGUSR1,SIGUSR1_handler);
+00094     
+00095     printf("*****************************************************************\n");
+00096     printf("*   Welcome to the asynchronous signal handling demonstration   *\n");
+00097     printf("*****************************************************************\n");
+00098     
+00099     printf("* This example demonstrates asynchronous signal handling using SIGUSR1 and SIGUSR2 signals.\n");
+00100     printf("* The example consists of two processes, the sigusr1 process and the sigusr2 process.\n");
+00101     printf("* The sigusr1 process handles the SIGUSR1 signal and sends a SIGUSR2 signal to the sigusr2 process.\n");
+00102     printf("* The sigusr2 process handles the SIGUSR2 signal and sends a SIGUSR1 signal to the sigusr1 process.\n");
+00103     printf("* The sigusr1 process opens a file and writes some text in it.\n");
+00104     printf("* The sigusr1 process then spawns the sigusr2 process and waits until SIGUSR1 is received from it.\n");
+00105     printf("* Once the sigusr1 process obtains a SIGUSR1 signal, it starts reading from the file and displays its\ncontent on the console.\n");
+00106     printf("* When all the file content is written, the sigusr1 process sends a SIGUSR2 signal to the sigusr2 process and prepares to exit.\n");
+00107     printf("* On other side the sigusr2 process keeps waiting for the SIGUSR2 signal from the sigusr1 process.\n");
+00108     printf("* On reception of the SIGUSR2 signal, the sigusr2 process prepares to exit.\n");
+00109     
+00110     printf("\nPress the Enter key to continue\n");
+00111     getchar();
+00112     
+00113     printf("****************** In the sigusr1 process ********************\n"); 
+00114   
+00115          
+00116     printf("\nOpening a file for read and write\n");
+00117     if((gfp = fopen(filename,"w+"))!=NULL)
+00118         {
+00119         printf("Successfully opened the file\n");
+00120         fprintf(gfp, "%s", "An asynchronous signal handling example using the SIGUSR1 and SIGUSR2 signals\n");
+00121         rewind(gfp);
+00122         printf("Writing to the file completed, preparing to start reading from the file\n");
+00123         
+00124         printf("Press the Enter key to spawn the sigusr2 process\n");
+00125         getchar();
+00126         
+00127         //Spawning sigusr2 process.
+00128         ret = posix_spawn(&chldProcsID,childProcess,NULL,NULL,argv,(char**)NULL);
+00129         if(ret != 0)     
+00130             {         
+00131             printf("\n*** failure posix_spawn ***\n");        
+00132             return EXIT_FAILURE;     
+00133             }
+00134         }
+00135     
+00136     printf("Waiting until SIGUSR1 is obtained from the sigusr2 process");
+00137     while(gVal)
+00138         {
+00139         printf(".");
+00140         sleep(delay);
+00141         }
+00142     
+00143     if(!fclose(gfp))
+00144         {
+00145         remove(filename);
+00146         gfp=NULL;
+00147         printf("The file was closed successfully.\n");
+00148         }
+00149     else
+00150         {
+00151         printf("File close failed.\n");
+00152         }
+00153     
+00154     printf("Press 'e'+Enter to exit from the sigusr1 process\n");
+00155     
+00156     while((gch=getchar())!= 'e')
+00157         {
+00158         if(gch == '\n')
+00159             continue;
+00160         else
+00161             printf("The wrong option was selected, please try again!!!\n");
+00162         }
+00163     return EXIT_SUCCESS;
+00164     }
+