int main(){
 	
 	char filename[30];
 	
 	FILE *in;
 	printf("Enter file you wish to open\n");
 	gets(filename); /* eeeeeah */
 	in = fopen(filename,"r");
 	printf("%s", 'in'); /* 'in' is not a valid character, not a valid string, nor a valid file */
 
  	/* Let's assume that you are trying to read from a file. First, don't write to it. */
 	/* You should be using fgets to get a string from a file or the stdin */
  	
 	if (in == NULL) { /* a little late for the check if you're already attempting to mess with it above */
                 printf("Error could not open %s\n", filename);
                 exit(1);
      }
 
 }

#include <stdio.h>
 
 int main(void)
 {
    const char filename[] = "file.txt";
    FILE *file = fopen(filename, "r");
    if(file)
    {
 	  char line [ BUFSIZ ];
 	  while(fgets(line, sizeof line, file))
 	  {
 		 fputs(line, stdout);
 	  }
 	  fclose(file);
    }
    return 0;
 }