pipes

[smart girl]

hi all

I am trying to be much familier with pipes

I tried to write a c program that generates the following output


from child:
I
want
to
print
this
line
twice

from parent:
I
want
to
print
this
line
twice

what I get is


from child:
I
want
to
print
this
line
twice

from parent:
I
I
I
I
I
I
I


my code is

Code:



#include<stdio.h>
#include<string.h>

int main(void){
int childpid,fd[2],nb,i,j;
char line[BUFSIZ]="I want to print this line twice";
char word[BUFSIZ];


pipe(fd);

childpid=fork();

if(childpid==0)
{
printf("from child:\n");

close(fd[0]);

char *token=strtok(line," ");

while(token!=NULL)
{
printf(" %s\n",token);

write(fd[1],token,(strlen(token)+1));

token=strtok(NULL," ");

}

}

else
{

wait(NULL);
printf("from parent:\n");



close(fd[1]);

for( i=0;i<7;i++){
nb=read(fd[0],word,sizeof(word));
printf("%s\n",word);

}

}

return 0;

}



can any one tell me what's wronge with this code and how to correct it?

[nagilum]

The problem is that the client writes null-terminated strings to the pipe, including the null-character at the end. The parent process waits for the child to finish and then reads all the data which was written to the pipe at once (if you print the nb-variable in the for loop you'll see that it is 0 for the last 6 times of the loop, it only reads data in the first iteration). So the word-variable contains the whole string in every iteration, plus null-characters after each word. The printf function only prints strings up to the null-character not beyond it, and that's why you only get the 'I' all the time.

[smart girl]

thanx for your reply the problem solved by reading from pipe using while loop :)