Member Avatar for Koji01

hi guys...i have a problem concerning strcmpi not equal while inside a while loop. Check out my code below:

#include<stdio.h>
#include<conio.h>
#include<stdlib.h>
#include<string.h>

main()
{
      char yr[4],new_yr[4];
      int x=0;
      FILE *fp1;
      printf("Enter Year: ");scanf("%s",new_yr);
      printf("\n");
      printf("You Entered Year %s\n\n",&new_yr);
      if(strlen(new_yr)==4)
      {
      fp1=fopen("year.txt","r");
      while(fscanf(fp1,"%s",yr)>0)
      {
                             if(strcmpi(yr,new_yr)!=0)
                             {

                             fp1=fopen("year.txt","a");

                             fprintf(fp1,"\n%s",new_yr);
                             fclose(fp1);
                             x=1;
                             }

      } 
      if(x==1) printf("Successfully added!!\n\n");
      else if(x==0)printf("year already exist!!\n\n");
      }

      else printf("Invalid Input!!");

      printf("\n\n");
      system("pause");
}

my program is about adding a new year and comparing it if there is no duplicate year the computer will add it to the file.
algorithm:

Enter Year: user input (e.g. 2007)

content of year.txt:
2003
2004
2005

if i enter 2007 the computer suppose to comparing it to 2003,2004,2005 if it has no duplicate it will add it to the file else the computer will say that Year already exist.

my problem is i think it doesnt compare, when i inputed 2007, the computer will add it plus the 2003...
and when i enter the year 2003 that i know already exist, computer will still add it.

can you guys tell me what is the problem in my code?

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  • Latest Post Latest Post by Koji01

Dani AI

Generated

There are three practical problems causing the behavior you saw: the code appends while it is still scanning (so any non-matching line causes an immediate append), it reopens the same FILE pointer inside the read loop (which corrupts the read), and the year buffers are too small for a 4-digit string plus the NUL terminator. was right to suggest a single flag and stopping when a match is found — add to that: validate input length, avoid unsafe "%s" reads, and only open the file for append after the whole file has been scanned.

Fix outline (apply in this order):

  • Read the user input safely (use fgets or a width-limited scan) and validate it is four digits.
  • Open the file for reading, iterate every existing line with fgets, trim newline/CR, compare (case-insensitive only if you need it), set an "exists" flag and break if found.
  • Close the read handle. If not found, open the file once in append mode and write the new year.
  • Always check fopen/fgets/fprintf return values and avoid reopening the same FILE while iterating.

Example pattern (concise, safer):

#include <stdio.h>
#include <string.h>
#include <ctype.h>

static int iequals(const char *a, const char *b) {
    while (*a && *b) {
        if (tolower((unsigned char)*a) != tolower((unsigned char)*b)) return 0;
        a++; b++;
    }
    return *a == *b;
}

/* read input into new_year[5] (4 digits + NUL), scan file with fgets, set found,
   then append once if not found. Check fopen/fgets returns in real code. */

Extra notes: use at least char new_year[5] (4 + NUL). Prefer fgets over scanf("%s") and validate digits with isdigit or strtol. strcmpi is nonstandard; on POSIX use strcasecmp and on MSVC use _stricmp (see man7 strcasecmp and ). Also handle CRLF when trimming lines on Windows.

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Member Avatar for Despairy

Add a boolean variable in the beginning of the program.
bool found=false;
( or if you don't use booleans just use an int with 0 or 1 like your X variable)

inside the while loop keep the strcmpi but like this
if(!strcmpi(yr,new_yr))
and change the boolean value to true and break; ( because you have found the same year already )

now when you check the for the boolean value , then perform the insertion to the file.
and you are done ( I hope ;) )

Member Avatar for Despairy

also if i'm not mistaken the
else printf("Invalid Input!!");
will never be true
since x is only 1 or 0.

give me an update

Member Avatar for Koji01

i'm sorry but i'm a newbie in this... bool found=false? i dont know where to put that on my code.

can you retype my code?

and the:
else printf("Invalid Input!!");
can be true because its pair up with:
if(strlen(new_yr)==4)
if the user inputs <4 or >4 strings, the statement will be true.

sorry for my bad english and bad indents.

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