parent send command line arguments to child - c

Question

I am writing a program that creates a pipe, forks, then the parent sends the command line arguments to the child one char at a time. The child is supposed to count them, and then the parent reaps the child and prints out how many arguments there were. Here is what I have so far:
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <string.h>
int main(int argc, char **argv)
{
pid_t pid;
int status;
int comm[2];
char buffer[BUFSIZ];
// set up pipe
if (pipe(comm)) {
printf("pipe error\n");
return -1;
}
// call fork()
pid = fork();
// fork failed
if (pid < 0) {
printf("fork error %d\n", pid);
return -1;
}
else if (pid == 0) {
// -- running in child process --
int nChars = 0;
close(comm[1]);
// Receive characters from parent process via pipe
// one at a time, and count them.
while(read(comm[0], buffer, sizeof(buffer)) != '\n')
nChars++;
// Return number of characters counted to parent process.
return nChars;
}
else {
// -- running in parent process --
int nChars = 0;
close(comm[0]);
// Send characters from command line arguments starting with
// argv[1] one at a time through pipe to child process.
char endl='\n';
for (int a = 1; a < argc; a++) {
for (int c = 0; c < strlen(argv[a]); c++) {
write(comm[1], &argv[a][c], 1);
}
}
write(comm[1], &endl, 1);
// Wait for child process to return. Reap child process.
// Receive number of characters counted via the value
// returned when the child process is reaped.
waitpid(pid, &status, 0);
printf("child counted %d chars\n", nChars);
return 0;
}
}
It seems to run endlessly. It must be stuck in one of the loops. What is going wrong?

Answer 1

Code:
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <string.h>
int main(int argc, char *argv[])
{
pid_t pid;
int status;
int comm[2];
char buffer[BUFSIZ];
// set up pipe
if (pipe(comm) < 0) {
printf("pipe error\n");
return -1;
}
// call fork()
if((pid = fork()) <0)
{
printf("fork error %d\n", pid);
return -1;
}
else if (pid == 0) {
// -- running in child process --
int nChars = 0;
close(comm[1]);
//printf("%d \n",BUFSIZ);
// Receive characters from parent process via pipe
// one at a time, and count them.
int n;
while( (n =read(comm[0], buffer, BUFSIZ)) >0)
{
buffer[n] = 0;
int oneChar, i = 0,endflag = 0;
while((oneChar = buffer[i])!=0)
{
// printf("%d\n",oneChar);
if(oneChar!=EOF)
nChars++;
else
{
endflag = 1;
break;
}
i++;
}
//printf("%s\n",buffer);
if(endflag)
break;
}
printf("nChar : %d",nChars);
// Return number of characters counted to parent process.
return nChars;
}
else {
// -- running in parent process --
//int nChars = 0;
close(comm[0]);
// Send characters from command line arguments starting with
// argv[1] one at a time through pipe to child process.
int a,c;
char endl='\n';
for ( a = 1; a < argc; a++) {
for ( c = 0; c < strlen(argv[a]); c++) {
write(comm[1], &argv[a][c], 1);
}
}
printf("write end\n");
int end = EOF;
write(comm[1],&end,4);
waitpid(pid, &status, 0);
printf("child counted %d chars\n", WEXITSTATUS(status));
return 0;
}
}