Function Freopen ()() in C

This guide covers function freopen ()() in c with practical context and easy-to-follow details. Use it to understand the subject and apply the information confidently.

Declaring the Function Freopen ()() in C

Below is the declaration for freopen () function in C:

 FILE * freopen ( const char * filename , const char * mode , FILE * stream ) 

Parameters

Filename - This is the string containing the file name to be opened.

Mode - This is the string containing the file access mode. Include:

Mode Description "r" Open a file to read. File must exist "w" Create an empty file to write. If a file with the same name already exists, its content is removed and the file is treated as a new blank file "a" Append to a file. With write operations, append data at the end of the file. The file is created if it does not already exist "r +" Open a file to write and read. File must exist "w +" Create an empty file to write and read "a +" Open a file to read and append

Stream - This is the pointer to a FILE object that identifies the Stream to be reopened.

Returns the value

If the file is successfully reopened, the function returns a pointer to an object that identifies the Stream, otherwise the null pointer is returned.

For example

The following C program illustrates the usage of freopen () function in C:

 #include int main () { FILE * fp ; printf ( "Dong text nay hien thi tren stdoutn" ); fp = freopen ( "baitapc.txt" , "w+" , stdout ); printf ( "Dong text nay duoc ghi vao baitapc.txtn" ); fclose ( fp ); return ( 0 ); } 

Compiling and running the above program will send the following line at STDOUT first:

After the call to freopen (), it binds STDOUT to baitp. Txt, so whatever we write at STDOUT will open baitapc. Txt. Therefore, the baitapc. Txt will have the following content:

Now you follow the contents of the above file by using the following C program:

According to Tutorialspoint

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