Not printing first 5 characters of the file - c

Question

The loop that reads from the file and prints the result is not printing the first 5 characters from all files read. If I print them 1 character at a time it works fine, but I'm reading floating point numbers from a file which I need to be processed later. The numbers are seperated by white space which is why I'm trying to print only when encountering white space.
here is my source code
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/wait.h>
#include <string.h>
#define BUFFER_SIZE 100
#define READ_END 0
#define WRITE_END 1
//main function
int main(int argc, char *argv[])
{
//process ids
int processIds[argc - 1];
int pipes[argc - 1][2];
char *fileNames[argc - 1];
int status;
//check if at least one data file
if (argc == 1)
{
return -1;
//end program
}
//get file names and store in array fileNames
int i;
for (i = 0; i < (argc - 1); i++)
{
fileNames[i] = argv[i + 1];
}
//create child processes
for (i = 0; i < (argc - 1); i++)
{
//make a pipe for communication
if (pipe(pipes[i]))
{
printf("bad pipe");
return -1;
}
//make a child process
processIds[i] = fork();
//check if child or paren process
if (processIds[i] == 0)
{
//child process
//close unused end
close(pipes[i][READ_END]);
//make file
FILE *dataset = fopen(fileNames[i], "r");
//test if file opened
if (dataset == 0)
{
printf("could not find/open file");
return -1;
}
//read and process file
char *x;
char *num = "";
int min, max;
while ((*x = fgetc(dataset)) != EOF)
{
if ((x == " ") || (x == "\t") || (x == "\n"))
{
//end of number
printf("A%s B%s", num, num);
num = "";
}
else
{
strcat(num, x);
}
//printf("%c", x);
}
printf("\n\n");
char msg[BUFFER_SIZE];
write(pipes[i][WRITE_END], msg, strlen(msg) + 1);
fclose(dataset);
exit(0);
}
else if (processIds[i] < 0)
{
//error
return -1;
}
else
{
//parent process closes write end of pipe
close(pipes[i][WRITE_END]);
}
}
//wait for children
for (i = 0; i < (argc - 1); i++)
{
//create a read buffer
char read_buf[BUFFER_SIZE];
//wait and get pid of completed child
int pid = wait(&status);
//find which child completed
int j = 0;
while (pid != processIds[j] && j < (argc - 1))
{
//pid not recognized, should not happen
if (j >= (argc - 1))
{
printf("bad pid");
return -1;
}
j++;
}
//read from completed child
read(pipes[j][READ_END], read_buf, BUFFER_SIZE);
}
return 0;
}

Answer 1

i can spot the following misses concerning your code:
1) Memory allocation
you need to allocate your num variable
example :
char *num = malloc(10);
2) returned type
'fgetc' doesn't return a pointer nor a char, so you should define
int x;
x = fgetc(dataset);
3) your condition is wrong
if ((x == ' ') || (x == '\t') || (x == '\n'))
note that ' ' is not " "
NOW as my suggestion to read those separate strings:
1) read all the file in buffer :
char buff[SIZE];
dataset= fopen("fileName.txt", "r");
if( dataset!= NULL ){
while ( !feof(fp ) ){
memset(buff, '\0', sizeof( buff) );
fgets(buff, SIZE, (FILE*)dataset);
}
fclose(dataset);
}
2) use strchr to find next space and print your strings
see example of use here