read file into array?

[conradin]

hi all,
Im trying to read a file into an array after its been assigned a memory location. but Im getting confuses about how to do that. I have a memory location named ptr, that I hope is the same size as the file being read in, but I have no idea what to do to get the data into the memory allocation. I would appreciate any help I can get.
I tried



#include <sys/types.h> //Specified in man 2 open
#include <sys/stat.h> //Allows for linux system Calls
#include <stdlib.h>
#include <unistd.h> //Specified in man 2 read
#include <errno.h> //Allows use of error numbers
#include <fcntl.h> //Specified in man 2 open
#include <stdio.h>


//StatFucntion taken from man 2 page
int main(int argc, char * argv[]){
struct stat sb;
if (argc > 2 || argc == 1) {
perror("Please include 1 and only 1 filename in the format:\n .<program> <filename> \n");
printf("errno = %d.\n", errno); //give error number
exit(EXIT_FAILURE); //Reads Success on exit??
}

if (stat(argv[1], &sb) == -1) {
perror("stat Error");
printf("errno = %d.\n", errno);
exit(EXIT_FAILURE);
}
//Show filesize: long long used because its the type used by stat.
printf("File size: %lld bytes\n",(long long) sb.st_size);

//assign memory with malloc: char used because it is 1 byte.
char *ptr = (char *) malloc(sb.st_size * sizeof (char));

if (ptr == NULL) {
perror("memory could not be allocated:\n");
printf("errno = %d.\n", errno);
exit(EXIT_FAILURE);
}
else {
//Open the file next:
int fp; //File open syntax:(<path> <readonly arg>)
if ((fp = open(argv[1],O_RDONLY))==-1){
perror("Open Crashed");
printf("errno = %d.\n", errno);
exit(EXIT_FAILURE);
}
else {

do {

int n = 0;
for (k=0; k < 255; k++){

}
////////////////////////////////////////////////////////////////////////
/////////////////////Not Sure what to put here//////////////////////////////
//////////////////////////////////////////////////////////////////////////


printf("%s Stuff:", ptr);
}while((read(fp,ptr,4096)!=0));

}


close(fp); /* Close the file */
free(ptr); /* Free the memory allocated in malloc */
ptr = NULL; /* The pointed-to-data must not be used again,*/
} /*unless re-assigned by using malloc again. */
return 0; //Program ended successfully.
}

[dwhitney67]

open(), close(), read(), etc are great for low-level I/O, however for your case, I would recommend using fopen(), fclose, fread(), etc.

Thus something like this would probably work for you:


...
//Open the file next:
FILE* fp = fopen(argv[1], "r");

if (fp == null)
{
perror("Open failed");
printf("errno = %d.\n", errno);
exit(EXIT_FAILURE);
}

// Read data from the file
size_t result = fread(ptr, 1, sb.st_size, fp);

if (result != sb.st_size)
{
// error reading file
}
...


By the way, if your file contains text, which presumably should be stored in a buffer containing a terminating null-character, then you should augment the number of bytes you allocate by 1.


char *ptr = malloc(sb.st_size + 1);