C Sorting of String arrays with exec() and fork (); -


could please explain me how for() , exec() works calling system calls sort? i've been reading around, still quite confused. data stored in .txt file looks like:

00-11-d9-20-aa-4e       951 cc-3a-61-df-4b-61       259 84-1b-5e-a8-bf-7f       82 74-e2-f5-17-96-89       829 84-1b-5e-a8-bf-7c       56

the space in center tab delimited. i'm trying sort out values based on second field decreasing exec() , sort(). no idea how to. i've called fork() complete sorting in separate process. then, returning parent print out results console.

int pid;     file *data;     char line[linesize];     data = fopen("results.txt", "r");     switch(pid = fork()){         case -1:             perror("fork()");             exit(1);             break;          case 0:             break;          default:             sleep(3);             while(fgets(line, sizeof line, data) != null){                 printf("%s", line);             }             printf("arrived @ parent");             break;     }     fflush(stdout);     exit(exit_success);

i've finished it,you can have try.

#include<stdio.h> #include<stdlib.h> #include<unistd.h> #include<fcntl.h> #define linesize 1024 int main() {     int pid;     file *data;     int fd;     char line[linesize];     data = fopen("results.txt","r");     switch(pid=fork())     {         case -1:             perror("fork()");             exit(1);             break;         case 0:             fd = open("results.txt",o_wronly);             dup2(fd,1); //output redirection stdout results.txt             execl("/usr/bin/sort",".","a.txt\0",null);             break;         default:             sleep(3);             while(fgets(line,sizeof(line),data) != null)             {                 printf("%s",line);             }             printf("arrived @ parent");             break;     }     return 0; }

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