File Management in C

File management in C involves operations like creating, opening, reading, writing, and closing files. C provides several functions through the stdio.h library for these tasks.

1. File Pointer (FILE *):

• A FILE * is a pointer to a file object used for all file operations.

• Example:

  FILE *fp;
  
  

2. Opening a File:

Use fopen() to open a file.

FILE *fopen(const char *filename, const char *mode);

• Modes:
  • "r": Read (file must exist).
  • "w": Write (creates a new file or truncates an existing one).
  • "a": Append (writes at the end of the file, creates if not existing).
  • "r+": Read and write.
  • "w+": Write and read (truncates existing file).
  • "a+": Append and read.

Example:

FILE *fp = fopen("file.txt", "r");
if (fp == NULL) {
    printf("Error opening file\\\\n");
}

3. Closing a File:

Use fclose() to close a file after completing operations.

fclose(fp);

4. Reading from a File:

• fgetc(): Reads a single character.

  char ch = fgetc(fp);
  
  

• fgets(): Reads a string from the file.

  char str[100];
  fgets(str, 100, fp);
  
  

• fscanf(): Reads formatted input (similar to scanf()).

  int num;
  fscanf(fp, "%d", &num);
  
  

5. Writing to a File:

• fputc(): Writes a single character.

  fputc('A', fp);