C fopen is a C library function used to open an existing file or create a new file. This tutorial guides you on how to use the fopen() function in the C program.
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 the name of the file to be opened.
- mode: The second argument is an access mode.
C fopen() access mode can be one of the following values:
| Mode | Description |
|---|---|
r
| It opens an existing text file. |
w
| It opens a text file for writing; a new file is created if the file doesn't exist. |
a
| It opens a text file for appending(writing at the end of an existing file) and creates the file if it does not exist. |
r+
| It opens a text file for reading and writing. |
w+
| It opens a text file for reading and writing, creates the file if it does not exist, and empties it if it already exists. |
a+
| It opens a text file for reading and appending and creates the file if it doesn't exist. Reading starts from the beginning, but writing can only append. |
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.
- Here in the above program,
wmeans that the file is being opened for writing, and if the file does not exist, a new file will be created.