• In C programming, file is a place on disk where a group of related data is stored.
  • When the program is terminated, the entire data is lost in C programming.
  • If you want to keep large volume of data, it is time consuming to enter the entire data.
  • But, if file is created, this information can be accessed using few commands.
  • There are large numbers of functions to handle file I/O in C language.
  • High level file I/O functions can be categorized as: Text file & Binary file.

File Operations:

• Creating a new file.
• Opening an existing file.
• Reading from and writing information to a file.
• Closing a file.

Functions:

I) Fopen ():

• This function is used to open a file to be accessed in the program which returns a FILE pointer.
• Once you've opened a file, you can use the FILE pointer to let the compiler perform input and output functions on the file.

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

fopen modes:

The allowed modes for fopen are as follows:

r - open for reading

w - open for writing (file need not exist)

a - open for appending (file need not exist)

r+ - open for reading and writing, start at beginning

w+ - open for reading and writing (overwrite file)

a+ - open for reading and writing (append if file exists)

II) Fclose ():

• This function is used to close the file opened using the file pointer passed to the function.
• fclose returns zero if the file is closed successfully.

Syntax: fclose(<file pointer identifier>);

Example: fclose(fp);

III) Feof ():

• This function returns true or false based on whether the pointer pointing to the file has reached the end of file or not.
• The pointer used to point the file has to be passed as a parameter to the function feof().

Syntax: feof(<file pointer identifier>)

Example: feof(fp)

IV) Fputc ():

• This function is used to put a character type data into the opened file using the fopen() function, pointed by a file pointer.
• The character to be put into a file as well as the file pointer are to be passed as the parameters to this function.

Syntax: fputc(<char type data>, <file pointer identifier>);

Example: fputc(c, fp);

V) Getc ():

• This function is used to get a character from the file pointed by the corresponding file pointer passed to the function.
• It is exactly opposite the fputc function.

Syntax: getc(file pointer identifier>);

Example: getc(fp);

VI) Rewind ():

• This function is used to rewind or bring the file pointer variable to point to the beginning of the file from wherever it is currently pointing in the file.

Syntax: rewind(<file pointer identifier>);

Example: rewind(fp);

VII) Fprintf ():

• This function is used to store the different data types in the file as the fputc() function is used to store the character in the file.
• This can be used to store integer, float, string etc types of data into the file opened.

Syntax: fprintf(<file pointer identifier>, “<format specifiers>”, <variable names>);

Example: fprintf(fp, “%d”, x);

VIII) Fscanf ():

• This function is used to read the different types of data as the getc() function is used to read a character from the file.
• This function can be used to read an integer, float string etc types of data into the file opened.

Syntax: fscanf(<file pointer variable>, “<format specifiers>”, <address of the variables in which the data is to be read>);

Example: fscanf(fp, “%d”, &x);