C fopen

File I/O

C fopen
C fopen function is used to open existing file or create a new file.

The basic format of fopen is:

Syntax:

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

Parameters

• filePath: The first argument is a pointer to a string containing name of the file to be opened.
• mode: The second argument is a access mode.

C fopen() access mode can be one of the following values:

Mode	Description
r	Opens an existing text file.
w	Opens a text file for writing, if file doesn’t exist then a new file is created.
a	Opens a text file for appending(writing at the end of existing file) and create the file if it does not exist.
r+	Opens a text file for reading and writing.
w+	Open for reading and writing and create the file if it does not exist. If the file exists then make it blank.
a+	Open for reading and appending and create the file if it does not exist. The reading will start from the beginning but writing can only be appended.

Return Value

C fopen function returns NULL in case of a 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 a 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.