Sprintf turning massive number into '4' - c

Question

I am trying to pass a pipe and need to convert its identifiers into strings. My problem is that currently sprintf is turning the identifiers into '4' as a string, which the process being passed to obviously can't use (note: it is being converted to 4 in the issuing process so the problem is not the pass itself)
Code:
Issuing process: (PipeC.c)
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
int main(){
int fd[2], B, C, D, numberRead, i, pipeReturn, *code;
char *arg[4];
char charsRead [10000], fdNumberAsString[256];
pipeReturn = pipe(fd);
if(pipeReturn < 0){ printf("error creating pipe\n"); return;}
sprintf(fdNumberAsString, "%d", fd[0]);
arg[0] = "PipeW1";
arg[1] = fdNumberAsString;
//printf("%d\n", fdNumberAsString);
sprintf(fdNumberAsString, "%d", fd[1]);
//printf("%d\n", fdNumberAsString);
arg[2] = fdNumberAsString;
arg[3] = NULL;
printf("PipeC - fd[0] = string: %s int: %d\n", arg[1], arg[1]);
printf("PipeC - fd[1] = string: %s int: %d\n", arg[2], arg[2]);
//printf("fd[0] = %d, fd[1] = %d\n", fd[0], fd[1]);
B = fork();
if(B == 0){
execv("PipeW1", arg);
printf("execv failed\n");
exit(1);
}
close(fd[1]);
numberRead = read(fd[0], charsRead, 5);
for(i = 0; i < 5; i++)printf("%c ", charsRead[numberRead]);
wait(code);
exit(0);
}
Created Process (PipeW1.c):
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
int main(int x, char** args){
printf("here\n");
int fd[2], pipeReturn, *ptr;
char num[256];
fd[0] = strtol(*(args+1), &ptr, 10);
printf("%d\n", fd[0]);
printf("PipeW1 - fd[0] = int: %d\n", fd[0], fd[0]);
fd[1] = atoi(*(args+2));
printf("PipeW1 - fd[0] = string: %s int: %d\n", fd[0], fd[0]);
printf("PipeW1 - fd[1] = string: %s int: %d\n", fd[1], fd[1]);
close(fd[0]);
write(fd[1], "12345", 5);
exit(0);
}
Resulting output:
[myname#myserver folder]$ PipeC
PipeC - fd[0] = string: 4 int: 1061374320
PipeC - fd[1] = string: 4 int: 1061374320
4
4
[myname#myserver folder]$```