UNIX for Dummies Questions & Answers

I have written the following program. The function of this prog is to read data from a file(source.c) and write into another file(dest.c) using pipes. I have just written a line in the source file.Im able to compile and run the program without errors. But the data is not written onto the other file(dest.c);
please help!!!!!!!!!!!!!!!!!!!!!!

[code]

#include <sys/wait.h>
#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>

int main()
{
int pfd[2],i=0,j=0;;
pid_t cpid;
char buf[20],ch,c;
FILE *fp1,*fp2;

fp1=fopen("source.c","r+");
if(fp1==NULL)
{
perror("Error opening source file\n");
}
while((ch=getc(fp1))!=EOF)
{
buf[i]=ch;
printf("i=%d ch=%c\n",i,ch);
i++;
}
buf[i] = '\0';
fclose(fp1);

if (pipe(pfd) == -1)
{
perror("pipe");
exit(EXIT_FAILURE);
}

cpid = fork();
if (cpid == -1)
{
perror("fork");
exit(EXIT_FAILURE);
}

if (cpid == 0)
{ /* Child reads from pipe */
char arr;
close(pfd[1]); /* Close unused write end */
fp2=fopen("dest.c","w+");
if(fp2==NULL)
{
perror("Error opening dest file\n");
_exit(1);
}
int i = 0;
while (i<=19)
{
read(pfd[0], &buf[i], sizeof(buf[i]));
c=buf[i];
putc(c,fp2);
i++;
}
close(pfd[0]);
_exit(EXIT_SUCCESS);
}
else
{ /* Parent writes argv[1] to pipe */
j=0;
close(pfd[0]); /* Close unused read end */
write(pfd[1], buf, strlen(buf));
j++;
close(pfd[1]); /* Reader will see EOF */
wait(NULL); /* Wait for child */
exit(EXIT_SUCCESS);
}
fclose(fp2);
}

Truly, I believe this quite interresting post to be more suitable here:
High Level Programming - The UNIX and Linux Forums
I would if I were you close this thread and open it there (dont duplicate posts...)

All the best

Thank you guys..... I got it fixed.
IT was happening cuz of the statement fclose(fp2) which i had written at the end of the parent process. As execution would never reach that place, i was having this problem.

The solution is we have to use the above mentioned statement at the end of the child process.

here goes the correct code.....

#include <sys/wait.h>
#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>

int main()
{
int pfd[2],i=0,j=0;;
pid_t cpid;
char buf[50],c;
FILE *fp1,*fp2;
int ch;

fp1=fopen("source.c","r+");
if(fp1==NULL)
{
perror("Error opening source file\n");
}
while((ch=getc(fp1))!=EOF)
{
buf[i]=ch;
i++;
}
buf[i] = '\0';
fclose(fp1);

if (pipe(pfd) == -1)
{
perror("pipe");
exit(EXIT_FAILURE);
}

cpid = fork();
if (cpid == -1)
{
perror("fork");
exit(EXIT_FAILURE);
}

if (cpid == 0)
{ /* Child reads from pipe */
close(pfd[1]); /* Close unused write end */
fp2=fopen("dest.c","w+");
if(fp2==NULL)
{
perror("Error opening dest file\n");
_exit(1);
}
int i = 0;
while (buf[i]!='\0')
{
read(pfd[0], &buf[i], sizeof(buf[i]));
c=buf[i];
putc(c,fp2);
i++;
}
fclose(fp2);
close(pfd[0]);
_exit(EXIT_SUCCESS);
}
else
{ /* Parent writes to pipe */
j=0;
close(pfd[0]); /* Close unused read end */
while(buf[j]!='\0')
{
write(pfd[1], &buf[j], sizeof(buf[j]));
j++;
}
close(pfd[1]); /* Reader will see EOF */
wait(NULL); /* Wait for child */
exit(EXIT_SUCCESS);
}
}


cheers
afser