Functionality of the updateCustomerAccountBalance has been completed

src/CustomerData.txt

@@ -1 +1,6 @@
-balance=500
+1234=example
+ID=1234
+forename=Max
+Surname=Mustermann
+password=example
+balance=1000

src/TempData.txt

@@ -1,5 +0,0 @@
-1234=example
-ID=1234
-forename=Max
-Surname=Mustermann
-balance=0

src/updateCustomerAccountBalance.c

@@ -1,51 +1,45 @@
 #include "updateCustomerAccountBalance.h"
 #include "currentCustomerAccountBalance.c"
 
-void deleteLineFromFile(int line){
-    FILE *fptr1, *fptr2;
-    char file1[] ="CustomerData.txt";
-    char file2[] ="TempData.txt";
-    char curr;
-    int del=line, line_number = 0;
-    fptr1 = fopen(file1,"r");
-    fptr2 = fopen(file2, "w");
-    curr = getc(fptr1);
-    if(curr!=EOF) {line_number =1;}
-    while(1){
-      if(del != line_number){
-        putc(curr, fptr2);
-        curr = getc(fptr1);
-        if(curr =='\n') line_number++;
-        if(curr == EOF) break;
+void deleteLineFromFile(const char* file_name, int line, const char* new_line){
+    FILE* file = fopen(file_name, "r");
+    if (file == NULL) {
+        printf("Error opening file!\n");
+        return;
+    }
+    char current_string[1024];
+    int current_line = 1;
+    char *temp_file_name = "temp.txt";
+    FILE* temp_file = fopen(temp_file_name, "w");
+    if (temp_file == NULL) {
+        printf("Error creating temp file!\n");
+        fclose(file);
+        return;
+    }
+    while (fgets(current_string, sizeof(current_string), file) != NULL) {
+        if (current_line == line) {
+            fprintf(temp_file, "%s", new_line);
         } else {
-        
+            fprintf(temp_file, "%s", current_string);
         }
-
+        current_line++;
     }
-    fclose(fptr1);
-    remove(file1);
-    fclose(fptr2);
-    rename(file2,"CustomerData.txt");
-    
+    fclose(file);
+    fclose(temp_file);
+    if(remove(file_name)!=0){
+        printf("could not remove the original file!");
+    } // Remove the original file
+    if(rename(temp_file_name, file_name)!=0){
+        printf("could not rename!");
+    } // Rename the temp file to the original file
 }
 
 void replaceBalanceInString(float replacementBalance, int currentLine) {
-    deleteLineFromFile(currentLine-1);
-    printf("deleting from line %i. balance will be replaced with %f", currentLine, replacementBalance);
     char newBalanceLine[MAX_LENGTH] = "balance=";
     char balance_as_string[MAX_LENGTH];
     sprintf(balance_as_string, "%g", replacementBalance); //converts replacement balance to string
     strcat(newBalanceLine, balance_as_string);
-    printf(newBalanceLine);
-
-    char buffer[MAX_LENGTH];
-    FILE *file = fopen("CustomerData.txt", "w"); 
-
-    for(int i=0;i<currentLine;i++){
-        fgets(buffer, MAX_LENGTH, file);
-    }
-    fprintf(file, newBalanceLine);
-    fclose(file);
+    deleteLineFromFile("CustomerData.txt",currentLine,newBalanceLine);
 }
 
 bool updateAvailableAccountBalance(int user_id, float changeInBalance){
@@ -78,12 +72,13 @@ bool updateAvailableAccountBalance(int user_id, float changeInBalance){
             strcpy(balance_String, buffer);
             currentLine+=4;
             availableBalance = fetchBalanceFromBalanceString(balance_String);
-            replaceBalanceInString(availableBalance+changeInBalance,currentLine);
+            
             keep_reading = false;
         }
 
     }
     fclose(file);
+    replaceBalanceInString(availableBalance+changeInBalance,currentLine);
 }
 
 int main(){

src/updateCustomerAccountBalance.h

@@ -5,5 +5,5 @@
 
 #define MAX_LENGTH 100
 bool updateAvailableAccountBalance(int user_id, float changeInBalance);
-void deleteLineFromFile(int lineNumber);
+void deleteLineFromFile(const char* file_name, int line, const char* new_line);
 void replaceBalanceInString(float replacementBalance, int currentLine);