Hi guys, how could i check in this code if a file already exists?
int main() {
FILE *file = fopen("./test.txt", "w");
int n = fprintf(file, "%s", "Hallo");
printf("%d\n", n);
}
#Check if a file already exists
limpid yew
fleet sinewBOT
worthy raptor
The question is "why do you want to check for the file's existence" to begin with?
worthy raptor
Doesn't tell the reason 😄
worthy raptor
fopen creates the file if it not exists
Not really. The second argument tells whether or not to create the file.
worthy raptor
Hence the question: why do you want to check for the file's existence?
Reworded: what use case are you trying to solve?
limpid yew
I mean the exercise says:
Check if a file exists , if not create it and write to it then print the bytes written to the file?
worthy raptor
Typically, you write your code for the general, working case and manage to have an exception or an error when things do not go as planned.
worthy raptor
I mean the exercise says:
Check if a file exists , if not create it and write t...
There is a problem with that algorithm...
And it is named "time of check to time of use": between the moment the system tells you the file doesn't exist and the moment you actually create it, the file may very well have been created.
frozen reef
Typically, you write your code for the general, working case and manage to have ...
Mh, maybe the exercise just want them to get familiar with file handling? Doesn't have to make much sense
worthy raptor
Yes, that's typical of assignments, I would say 🙂
frozen reef
There's an approach you could take: fopen the file in read mode, that particular open would fail if the file doesn't exist
runic quest
Have you searched for documentation on fopen?
limpid yew
jes
i could do it with fopen in read mode
then check for null and in this branch i could open it in write mode?
seems kinda weird
worthy raptor
Do you have to use fopen() ?
Because if not, then there's a way for the system to return an error if the file already existed while you wanted to create it. And it involves using open() instead with flags O_EXCL and O_CREAT. Read up man 2 open if that suits you.
limpid yew
jesss ill check it out
fleet sinewBOT
fringe oriole
#include <stdlib.h>
int main() {
int result = perform_operation();
if (result != 0) {
exit(EXIT_FAILURE); // Terminate program with a failure status
}
return 0;
}
Why is it showing error in online compiler pls help me
crude abyss
#include <stdlib.h>
int main() {
int result = perform_operation();
if (...
What's the error message?
crude abyss
<@598173536405946368>
Seems like you haven't defined perform_operation()
If you copied it from some website it's probably a placeholder
fringe oriole
If you copied it from some website it's probably a placeholder
Yse, Sir
crude abyss
Yse, Sir
I'd assume the function performs some random operation and returns an int, 0 if the operation was successful and some other number if otherwise
If you want to test just the failure status you can simply define perform_operation() to return 1 or some such
muted flare
