Administrace komentářů

Zkusil jsem tu rouru otevrit open(), aby mi dala cislo file descriptoru, a tudiz by se dalo nadale postupovat jako u nepojmenovane roury, jenze mi to pri pouziti parametru:

./fifo ls -la @ grep -v .c

uz po otevreni roury pro zapis

fw = open(fifo_name, O_WRONLY);

hazi chybu:

grep: (standardní vstup): Chybný popisovač souboru

Coz je divne, ze mi to hlasi zrovna grep pri otevreni roury teprve por zapis...

To same potom pri otevreni roury pro cteni:

ls: chyba při zápisu: Roura přerušena (SIGPIPE)

Promenne fr ani fw se mi neinicailzuji, po open() maji hodnotu 0.

Pri kompilaci pak dostavam pochopitelne:

fifo.c: In function ‘main’:

fifo.c:66:18: warning: ‘fw’ may be used uninitialized in this function [-Wuninitialized]
fifo.c:82:18: warning: ‘fr’ may be used uninitialized in this function [-Wuninitialized]

DOsavadni kod je takovyto:

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

	if (argc < 2) {
	
		printf("Programme must be run with with arguments and using pipe shell symbol as a delimiter!\n"
			"For example: ./fifo ls -la @ grep -v .c\n");
		exit(1);
	}
        
        int count, fw, fr, status;
        char command1[50];
        char command2[50];
        char arguments1[50];
        char arguments2[50];
        char* fifo_name = "/tmp/myfifo";
        
        strcpy(command1, argv[1]);
        strcpy(arguments1, " ");
        strcpy(arguments2, " ");

        count = 2;
        
        for (; count < argc; count++) {
                        
            if (strcmp(argv[count], "@") == 0) {
                
                break;
            }
            
            strcat(arguments1, argv[count]);
            strcat(arguments1, " ");
        }
        
        arguments1[strlen(arguments1)-1] = '\0';  //removing ending space       
        strcat(command1, arguments1);      
        strcpy(command2, argv[count+1]);
        count += 2;


        for ( ; count < argc; count++) {
            
            strcat(arguments2, argv[count]);
            strcat(arguments2, " ");
        }
        
        arguments1[strlen(arguments2)-1] = '\0'; 
        strcat(command2, arguments2);
                
        status = mkfifo(fifo_name, S_IWUSR | S_IRUSR | S_IRGRP | S_IROTH);
        
        if(status == -1) {

                perror( "Mkfifo failed" );
        	exit(1); 
        }

	pid_t pid = fork();
	
	if (pid == -1) {
	   
            return -1;  
        }

	if (pid == 0) {
	  
            close(fw);
            fr = open(fifo_name, O_RDONLY);
            unlink(fifo_name);
                    
            if(fr == -1) {
                printf("Could not open the pipe for reading.\n");
                exit(1);
            }
            
            
            dup2(fr, STDIN_FILENO);
            close(fr);
            system(command2); 
            unlink(fifo_name);
	}

	else {
	           
            close(fr);
            fw = open(fifo_name, O_WRONLY);
                               
            if(fw == -1) {
                        printf("Could not open the pipe for writting.\n");
                        exit(1);
            }    
            
                      
            dup2(fw, STDOUT_FILENO);
            close(fw);
            system(command1);
            unlink(fifo_name);    
	}  
	
	return EXIT_SUCCESS;
}

Takze chce to vyresit deskriptory, mozna pouzit jinou fce nez open. Jenze kdyz pouziju fopen(), tak da se nejak jejich vysledek typy FILE* predelat na int a pouzit jako filedeskriptor? To je jediny mozny co me napada...