Thread: How to redirect using pipelines

Are you trying to redirect to descriptor 2 (stderr), or just a file called "2" ?

You're half-way there based on your previous thread.
All you need now is to dup() fd onto descriptor 1 (stdout) or 2 (stderr) as you like.

hum,
it's not much but hope its helps a little, that compiles, and runs.

Code:

#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
       
       
int main(){
  char *args[] = {"sort", "myshell.c", ">", "2"};
  int size = sizeof(args)/sizeof(args[0]);
  int rw[2];//pipes
  int i;
  pipe(rw);
  //FILE* file;
 
  char file[30];
 
 
  for(i = 0; i < size; i++){
       // if(!strcomp(args[i], ">")){
        if(!strcmp(args[i], ">")){ //Linux not windows 
                strcpy(file,args[i+1]);
                printf("%s\n", file);
                //file = args[i+1];//getting the file name (in this case 2)
        }
  }
 
 /*
 // not really sure what you're doing here 
   if((pid = fork()) == 0){//child
 
 
        int fd  = open(file, O_CREAT | O_RDWR);
 
 
  }else{//parent
    //printf("Parent\n");
 
 }
 */
 
 
return 0;
}

fork
The fork() System Call

open
http://www.techytalk.info/linux-syst...nd-write-file/

redirect

Code:

userx@slackwhere:~
$ touch 2
userx@slackwhere:~
$ echo "hey stdout" > 2
userx@slackwhere:~
$ cat 2
hey stdout
userx@slackwhere:~
$ sort ~/bin/term2.c >> 2
userx@slackwhere:~
$ cat 2  
hey stdout
    //printf("Parent\n");
 
 
 
 
 
 
 
 
 
 
 
       
       
                //file = args[i+1];//getting the file name (in this case 2)
                printf("%s\n", file);
                strcpy(file,args[i+1]);
        if(!strcmp(args[i], ">")){ //Linux not windows 
        int fd  = open(file, O_CREAT | O_RDWR);
        }
       // if(!strcomp(args[i], ">")){
   if((pid = fork()) == 0){//child
  //FILE* file;
  char *args[] = {"sort", "myshell.c", ">", "2"};
  char file[30];
  for(i = 0; i < size; i++){
  int i;
  int rw[2];//pipes
  int size = sizeof(args)/sizeof(args[0]);
  pipe(rw);
  }
  }else{//parent
 */
 /*
 // not really sure what you're doing here 
 }
#include <fcntl.h>
#include <stdio.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
int main(){
return 0;
}

First, you do this

Code:

        if(!strcomp(args[i], ">")){
                file = args[i+1];//getting the file name (in this case 2)
                args[i] = NULL;
        }

This is so you now have an argv compatible with the exec() functions.

Then you call dup() to map stdout to the fd you just opened (see manual pages posted previously)

Then finally, something like
execvp( argv[0], argv );