CODEWITHSUNDEEP
cunixprintffopen
ValeMarz
ValeMarz

Reputation: 101

How to overwrite a text file?

I'm coding on Unix. I've a text file as output. How can I overwrite the content every time I call a function?

Example:

functionA(){
    fp = fopen("text.txt",someflag);
    ...
    ...blabla
    ....
    fprintf(fp,"some new text");
}

So by calling functionA, I should have text.txt with new content.

For someflag, I've already tried a, ab, and w+, but none with the result I want. (ab appends new text, w+ open the file, but fprintf doesn't work). I'm using C on unix.

Upvotes: 1

Views: 6664

Answers (1)

Tim
Tim

Reputation: 9259

Flag "w" should overwrite the existing file.

See this documentation for details, specifically:

The mode argument points to a string. If the string is one of the following, the file shall be opened in the indicated mode. Otherwise, the behavior is undefined.

  • r or rb: Open file for reading.
  • w or wb: Truncate to zero length or create file for writing.
  • a or ab: Append; open or create file for writing at end-of-file.
  • r+ or rb+ or r+b: Open file for update (reading and writing).
  • w+ or wb+ or w+b: Truncate to zero length or create file for update.
  • a+ or ab+ or a+b: Append; open or create file for update, writing at end-of-file.

Upvotes: 5

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