Easy To Learn Opening a file In C Language

Opening a file In C Language

C communicates with files using a new data type called a file pointer. This type is defined within stdio.h, and written as FILE *. A file pointer called output_file is declared in a statement like

Syntax: FILE *output_file;

If we want to store data in a file into the secondary memory, we must specify certain things about the file to the operating system. They include the filename, data structureâ€¦

The general format of the function used for opening a file is

Syntax :

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

Here filename is the name of the file to be opened and mode specifies the purpose of opening the file. Mode can be of following types,

*fp is the FILE pointer (FILE *fp), which will hold the reference to the opened(or created) file.

Mode	description
r	opens a text file in reading mode
w	opens or create a text file in writing mode.
r+	opens a text file in append mode
	opens a text file in both reading and writing mode
w+	opens a text file in both reading and writing mode
a+	opens a text file in both reading and writing mode
rb	opens a binary file in reading mode
wb	opens or create a binary file in writing mode
ab	opens a binary file in append mode
rb+	opens a binary file in both reading and writing mode
wb+	opens a binary file in both reading and writing mode
ab+	opens a binary file in both reading and writing mode

Return value :

C open function returns NULL in case of failure, and returns a FILE Stream Pointer on success

Example :

#include<stdio.h>
int main()
{
 FILE *fp;
 fp = fopen(“fileName.txt”, “w”);
 return 0; 
}

• The above example will create file called fileName.txt

• The “w” means that the file is being opened for writing, and if the file does not exist then new file will be created.

C - Language Tutorial