Hi all,

I'd like to perform the piping utility as performed by the unix shell..
It should support multiple piping.
I was told that it can be done using recursion.
can someone help?

ex: ps -ef | grep httpd | sort | wc
(or)
ls -ltr | wc

etc....

assuming commands are in an array called "COMMAND_ARRAY[i][0] and its arguments are in COMMAND_ARRAY[i][1..n]

Please help!

What have you done yourself ? For example, what documentation regarding pipes have you read ?

You can start from here: http://www.cs.uleth.ca/~holzmann/C/s...eforkexec.html .

Hi,

I have done the following..I have tried to write a code that handles two commands with one pipe...

void executePipeFunctionality()
{
int fildes1[2];
int fildes2[2];
pid_t first, second, pid;
int i = 0, index = 0, initIndex1 = 0, initIndex2 = 0, innerIndex = 0;
char* arg1[MAXITEM] = {NULL};
char* arg2[MAXITEM] = {NULL};
int returnValue = 0,status=0;
printf("NUM_PIPE_INSTANCES: %d\n", NUM_PIPE_INSTANCES);
printf("INPUT_SIZE: %d\n", INPUT_SIZE);
//printf("##1##");
arg1[0] = (char*)malloc(sizeof(char) * strlen(GLOBAL_WORD_ARRAY[0]));
arg1[1]=(char*)malloc(sizeof(char) * strlen(GLOBAL_WORD_ARRAY[1]));
arg2[0]=(char*)malloc(sizeof(char) * strlen(GLOBAL_WORD_ARRAY[3]));
arg2[1]=(char*)malloc(sizeof(char) * strlen(GLOBAL_WORD_ARRAY[4]));


//printf("hi");
strcpy(arg1[0],GLOBAL_WORD_ARRAY[0]);
strcpy(arg1[1],GLOBAL_WORD_ARRAY[1]);
strcpy(arg2[0],GLOBAL_WORD_ARRAY[3]);
strcpy(arg2[1],GLOBAL_WORD_ARRAY[4]);

//printf("^^%s^^.^^%s^^.^^%s^^",arg1[0],arg1[1],arg2[0]);
if(fork()==0)
{
pipe(fildes1);

/* We are the child process, but since we have TWO commands to exec we
* need to have two disposable processes, so fork again */
switch (fork()) {

case 0:
close(fildes1[1]); /* the other side of the pipe */
dup2(fildes1[0], 0); /* automatically closes previous fd 0 */
close(fildes1[0]); /* cleanup */
/* exec tr */
returnValue=execvp(arg2[0], arg2);


default:






close(fildes1[0]); /* the other side of the pipe */
dup2(fildes1[1], 1); /* automatically closes previous fd 1 */
close(fildes1[1]); /* cleanup */

returnValue=execvp(arg1[0], arg1);

}

}
else
{
wait(&status);
}

}

I have implemented 2 pipes in c...........

it will get you the value for :-

ls -l | tee f1 | wc -l

where f1 is a file created by tee...

Here goes the program..........

#include <stdio.h>
#include <string.h>
#include <fcntl.h>
#include<malloc.h>
#include<ctype.h>
#include <unistd.h>


int main()
{


int fd[2], fd1[2];

int pid, pid2, pid3;

if (pipe(fd) == -1) {
printf("Error: Pipe failed.\n");
return 1;
}
if (pipe(fd1) == -1) {
printf("Error: Pipe failed.\n");
return 1;
}

if ((pid = fork()) < 0) {
printf("Error: Fork failed.\n");
return 1;
}

if (pid == 0) {

// child process
close(fd1[1]);
close(fd[1]);
dup2(fd1[0], 0);
close(fd1[0]);
char *argv1[2];

argv1[0]="wc";
argv1[1]="-l";
argv1[2]=NULL;
execvp(argv1[0],argv1);

}
else {
if ((pid2 = fork()) < 0) {
printf("Error: Fork failed.\n");
return 1;
}
if (pid2 == 0) {
// child process

close(fd[1]);
close(fd1[0]);
dup2(fd[0], 0);
close(fd[0]);

dup2(fd1[1], 1);
close(fd1[1]);



char *argv2[2];
argv2[0]="tee";
argv2[1]="f1";
argv2[2]=NULL;


execvp(argv2[0],argv2);


}
else
{
if ((pid3 = fork()) < 0)
{
printf("Error: Fork failed.\n");
return 1;}
if (pid3 == 0) {
// child process
close(fd[0]);
close(fd1[1]);
dup2(fd[1],1);
close(fd[1]);
char *argv3[2];
argv3[0]="ls";
argv3[1]="-l";
argv3[2]=NULL;

execvp(argv3[0], argv3);
printf("Error: execv failed.\n");
return 1;
}

else
{


wait(NULL);
}

}

}
return 0;
} // for main

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may be u can convert it into recursion...........m also working on it............

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