Example of how to clear a file in C Language

Example of how to clear a file in C Language

/********************************************************************* * Author  : Samson * Date    : 02/12/2015 * Test platform: *              3.13.0-24-generic *              GNU bash, 4.3.11(1)-release  * *******************************************************************/

How can I use C to clear the content of a file directly?

The answer is in the following program code:

# Include
# Include
# Include
# Include
# Include

# Define PATHNAME "./test"
Int main ()
{
Int ret = open (PATHNAME, O_WRONLY | O_TRUNC );
If (ret =-1)
{
Printf ("open file is fail! \ N ");
Return-1;
}
Close (ret );
Return 0;
}

There is a file named test in the current directory. Run the ll command to check the file size:

Ufo @ ufo:/tmp $ ll test

-Rw-r -- 1 ufo 293 February 12 17:05 test
Ufo @ ufo:/tmp $ gcc testwrite. c

Ufo @ ufo:/tmp $./a. out

Run the command to check the size of the test file, that is, it is already 0, and no content is displayed when cat test is used.

Ufo @ ufo:/tmp $ ll test
-Rw-r -- 1 ufo 0 February 12 17:05 test

The key lies in the oflag parameter in the open function. You can use man 2 open to view the description of the open function,

O_WRONLY: indicates to open the file as write only

O_TRUNC: indicates that if the file with the parameter name pathname in open exists and only writes or reads/writes are successfully opened, the length of the file will be shortened to 0. In this way, the object content is cleared.