arrays - Method to safely get a string in C -

i'm new c , want write function safely prompts user string , returns it. while think have safety part handled, can't return string main method , print out. here code

//method safely read user input char * getfilename(char* filename) {     char* str[50];     int isvalid = 0;     while (isvalid == 0) {         isvalid = 1;         printf("enter file name: ");         fgets(str, 50, stdin);         if (strlen(str) == 49 && str[48] != '\n') { //http://stackoverflow.com/questions/21691843/how-to-correctly-input-a-string-in-c             isvalid = 0;             if (strlen(str) > 0 && str[strlen(str) - 1] != '\n') {//http://stackoverflow.com/questions/35136026/simple-loops-and-string-length-in-c?noredirect=1#comment58000759_35136026                 printf("error! string long\n\n");                 {                     fgets(str, 50, stdin);                 } while (strlen(str) > 0 && str[strlen(str) - 1] != '\n');             }         }         (int = 0; < strlen(str); i++) {             if (str[i] == '%') {                 printf("error: attempted string format attack\n\n");                 isvalid = 0;             }         }     }     (int = 0; < strlen(str); i++) {         filename[i] = str[i];     }     return filename; }  int main() {     //opening text file     char filename[50];     getfilename(filename);     printf(filename);      printf("press enter continue...");     getchar();     //     return 0; } 

running code prints result

and have no idea why. appreciated!

because never copy null terminator. this

for (int = 0; < strlen(str); i++)     filename[i] = str[i]; 

only copies characters, not null terminator. use strcpy() since included string.h overuse strlen().

try this

int i; (i = 0; str[i] != '\0' ; ++i)     filename[i] = str[i]; filename[i] = str[i]; 

and should work expect it, , avoid using strlen() that.

you have major problem,

char *str[50]; 

is array of 50 char pointers, , doesn't seem want instead

char str[50]; 

your code complicated , hard understand, think want

#include <stdio.h> #include <string.h>  char * getfilename(char *str, size_t size) {     int isvalid = 0;     while (isvalid == 0)     {         size_t length;         isvalid = 1;          printf("enter file name: ");         if (fgets(str, size, stdin) == null)             return null;         length = strlen(str);         if ((length == size - 1) && (str[size - 2] != '\n'))         {             isvalid = 0;             if ((length > 0) && (str[length - 1] != '\n'))             {                 printf("error! string long\n\n");                 continue;             }         }          if (strchr(str, '%') != null)         {             printf("error: attempted string format attack\n\n");             isvalid = 0;         }     }     return str; }  int main() {     char array[100];     if (getfilename(array, sizeof(array)) == null)         fprintf(stderr, "error: input problem?\n");     else         printf(array);     return 0; }