File Handling in C: Functions, Structures, and File Splitting

Posted on Mar 21, 2025 in Computers

File Handling in C: A Practical Explanation

File Operations

Data type: FILE *

fopen: This function opens or creates a file physically.

fich = fopen("filename", "mode");

Opening modes: "r" (read), "w" (write), "a" (append), "+" (update)

• fclose(tab);
• character = getc(tab);
• fgets(string, length or size, fich);
• putc(character, cards);
• fputs(string, cards);
• EOF: End Of File
• rewind(tab)

Structures and Records

Creating variables of type STRUCTURE OR RECORD:

struct reg_alumno alumno1;

Access fields using dot notation. Example: alumno1.edad

Arrow notation -> (If the parameter is input/output). Example: alumno1->age

File Writing and Reading

fwrite: Procedure with parameters:

1. Variable that contains the data (&alumno1).
2. Number of bytes that we entered into the file. sizeof function: Returns the number of bytes of a data type. sizeof(struct reg_alumno)
3. Fixed left as a 1 (indicates that we want to enter data: a student).
4. File where we enter the data (cards).

fwrite(&alumno1, sizeof(struct reg_alumno), 1, cards);

fread: Procedure with 4 parameters.

fread(&alumno1, sizeof(struct reg_alumno), 1, cards);

struct reg_alumno { char name[12]; char surname[25]; int age; float notaMedia; };

Switch Statement Example

int option; switch (option) { case 1: printf("number 1"); }

String Manipulation Function

Function to Delete Character at Position

int funcionborrarpos(char str[20], char elim)

int main() {
 char elim;
 char str[20];
 printf("\n Enter a string:");
 gets(str);
 printf("\n Enter one character to delete: ");
 scanf("%c", &elim);
 printf("\n");
 funcionborrarpos(str, elim);
 printf("\n outside the function ");
 getch();
}

int funcionborrarpos(char str[20], char elim) {
 printf("\n Inside the function");
 printf("\n%c", str);
 int i;
 for (i = 0; str[i] != '\0'; i++) {
 if (str[i] == elim) {
 while (str[i] != '\0') {
 str[i] = str[i + 1];
 i++;
 }
 }
 }
 printf("\n%c", str);
 getch();
}

File Splitting Functions

void mayusculas(FILE *fp);

void lowercase(FILE *fp);

void numbers(FILE *fp);

/* file * is better to fichorigen, fichmayus, fichminus and fichnume. -create a procedure to split files .*/

int main() {
 char letter;
 char name[25];
 printf("\n Separate mayus minussy nums:");
 printf("\n --");
 printf("\n Enter the name of the file you have open (and the extension...): \n-> ");
 gets(name);
 getch();
 FILE *fp;
 fp = fopen(name, "r");
 if (fp == NULL)
 printf("\nError");
 else {
 printf("Ok open-file ");
 printf("\n - ");
 printf("\n ...");
 mayusculas(fp);
 rewind(fp);
 lowercase(fp);
 rewind(fp);
 numbers(fp);
 fclose(fp);
 }
 getch();
}

void mayusculas(FILE *fp) {
 char car;
 FILE *fmayus;
 fmayus = fopen("mayusculas.txt", "w");
 rewind(fp);
 if (fmayus == NULL) {
 printf("\n Error in mayusculas.txt");
 }
 else {
 printf("\n mayusculas.txt open file");
 car = getc(fp);
 while (!feof(fp)) {
 if ((car >= 'A') && (car <= 'Z')) {
 putc(car, fmayus);
 }
 car = getc(fp);
 }
 fclose(fmayus);
 }
}

void lowercase(FILE *fp) {
 char car;
 FILE *fminus;
 fminus = fopen("minusculas.txt", "w");
 rewind(fp);
 if (fminus == NULL) {
 printf("\n Error in minusculas.txt ");
 }
 else {
 printf("\n minusculas.txt open file ");
 car = getc(fp);
 while (!feof(fp)) {
 if ((car >= 'a') && (car <= 'z')) {
 putc(car, fminus);
 }
 car = getc(fp);
 }
 fclose(fminus);
 }
}

void numbers(FILE *fp) {
 char car;
 FILE *fnum;
 fnum = fopen("numeros.txt", "w");
 rewind(fp);
 if (fnum == NULL) {
 printf("\n Error in numeros.txt");
 }
 else {
 printf("\n numeros.txt open file");
 car = getc(fp);
 while (!feof(fp)) {
 if ((car >= '0') && (car <= '9')) {
 putc(car, fnum);
 }
 car = getc(fp);
 }
 fclose(fnum);
 }
}