#include<stdio.h>
int main(){	FILE *in=fopen("name_of_file.txt","r");	char c;	while((c=fgetc(in))!=EOF)	putchar(c);	fclose(in);	return 0;
}

#include <stdio.h>
#define n 1024 // n bytes
int main(void) {	FILE *fp; size_t numread; if ((fp = fopen("yourfile.xy", "rb") != NULL) {	char buffer[n]; numread = fread(buffer, sizeof(*buffer), n, fp);	printf("Read %d Bytes: %s", numread, buffer);	fclose(fp);	return 0; } return -1;
}

// C program to implement
// the above approach
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
 
// Driver code
int main()
{
    FILE* ptr;
    char ch;
 
    // Opening file in reading mode
    ptr = fopen("test.txt", "r");
 
    if (NULL == ptr) {
        printf("file can't be opened \n");
    }
 
    printf("content of this file are \n");
 
    // Printing what is written in file
    // character by character using loop.
    do {
        ch = fgetc(ptr);
        printf("%c", ch);
 
        // Checking if character is not EOF.
        // If it is EOF stop eading.
    } while (ch != EOF);
 
    // Closing the file
    fclose(ptr);
    return 0;
}

#include <stdio.h>
#include <stdlib.h>
int main()
{ int num; FILE *fptr; if ((fptr = fopen("C:\\program.txt","r")) == NULL){ printf("Error! opening file"); // Program exits if the file pointer returns NULL. exit(1); } fscanf(fptr,"%d", &num); printf("Value of n=%d", num); fclose(fptr); return 0;
}

FILE *in_file  = fopen("name_of_file", "r"); // read only 
          FILE *out_file = fopen("name_of_file", "w"); // write only 
           
          // test for files not existing. 
          if (in_file == NULL || out_file == NULL) 
            {   
              printf("Error! Could not open file\n"); 
              exit(-1); // must include stdlib.h 
            } 
           
          // write to file vs write to screen 
          fprintf(file, "this is a test %d\n", integer); // write to file 
 
          fprintf(stdout, "this is a test %d\n", integer); // write to screen  
          printf(         "this is a test %d\n", integer); // write to screen  
 
          // read from file/keyboard. remember the ampersands!  
          fscanf(file, "%d %d", &int_var_1, &int_var_2);  
 
          fscanf(stdin, "%d %d", &int_var_1, &int_var_2);  
          scanf(        "%d %d", &int_var_1, &int_var_2);

#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>
#define MAXLENGTH 256
int display(char* FILE) { int f = open(FILE, O_RDONLY); // we open the file in read only if (f == -1) { // open() returns -1 if there's an error perror("open"); close(f); return 1; } else { char buffer[MAXLENGTH]; int r = read(f, &buffer, MAXLENGTH); if(r == -1){ // read() returns -1 if there's an error perror("read"); close(f); return 2; } else { write(1, buffer, r); close(f); return 0; } }
}
int main(void) { display("file.txt"); return 0;
}