CODEWITHSUNDEEP
cfwrite
Lightsout
Lightsout

Reputation: 3757

is fclose() call needed when writing to file

Say I'm writing to a file but I want to end the write by turning off the power to the machine, would that be a problem that the fclose() function didn't get called?

FILE *f = fopen("file.txt", "w");
if (f == NULL)
{
    printf("Error opening file!\n");
    exit(1);
}

/* print some text */
while(1){
//write something...
}
//Dont want to call this
fclose(f);

Upvotes: 0

Views: 518

Answers (1)

paddy
paddy

Reputation: 63471

Short answer: no, not as written, if there is any kind of buffering. And if no buffering, also maybe no.

The buffering mode can be controlled with setvbuf. You can also periodically call fflush to flush the buffers.

However, regardless of how you manage the buffering, control is transferred to the OS kernel I/O scheduling, and then to the hardware (which may have its own buffering).

The file I/O routines in <stdio.h>, to my knowledge, don't give you control at a low enough level to be absolutely certain your data is written upon return from a call such as fflush.

Note that here I'm talking about sudden unexpected power loss.

Upvotes: 0

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