Communities

Writing
Writing
Codidact Meta
Codidact Meta
The Great Outdoors
The Great Outdoors
Photography & Video
Photography & Video
Scientific Speculation
Scientific Speculation
Cooking
Cooking
Electrical Engineering
Electrical Engineering
Judaism
Judaism
Languages & Linguistics
Languages & Linguistics
Software Development
Software Development
Mathematics
Mathematics
Christianity
Christianity
Code Golf
Code Golf
Music
Music
Physics
Physics
Linux Systems
Linux Systems
Power Users
Power Users
Tabletop RPGs
Tabletop RPGs
Community Proposals
Community Proposals
tag:snake search within a tag
answers:0 unanswered questions
user:xxxx search by author id
score:0.5 posts with 0.5+ score
"snake oil" exact phrase
votes:4 posts with 4+ votes
created:<1w created < 1 week ago
post_type:xxxx type of post
Search help
Notifications
Mark all as read See all your notifications »
Q&A

Welcome to Software Development on Codidact!

Will you help us build our independent community of developers helping developers? We're small and trying to grow. We welcome questions about all aspects of software development, from design to code to QA and more. Got questions? Got answers? Got code you'd like someone to review? Please join us.

Comments on Why does fopen return NULL?

Parent

Why does fopen return NULL?

+3
−2
#include<stdio.h>
#include<stdlib.h>
int main (void){
  
   FILE *cfPtr; 
   char name[15];
   int ID;
   if ((cfPtr = fopen("draft.txt","w")) == NULL){
    printf("File could not be opened...\n"); //program gives me this as an output
   }

} 

Output:

File could not be opened...

History
Why does this post require moderator attention?
You might want to add some details to your flag.
Why should this post be closed?

1 comment thread

From one of the documentation pages for fopen... (1 comment)
Post
+6
−0
  • The simple explanation would be that you simply don't have write access to the path, which is one possibility.

  • Another weird phenomenon that may happen is that you are running a very old C compiler and it can't find fopen - because you did forget to #include <stdio.h>.

    When this happens on modern compilers, you get a compiler error. On very old compilers (the "ANSI/C90 standard") the compiler would instead cook up some dumb initiative of its own and treat the function as if it returns int. This could create very strange and subtle bugs.

    You could avoid such bugs by updating to the latest version of your C compiler. In case of gcc, clang or icc compilers you should also follow this advise: What compiler options are recommended for beginners learning C?

Unrelated to your question fflush(stdin); is undefined behavior and rarely the correct solution. Instead you should just ensure to consume the line feed character after taking the input. (For example by a getchar() call or by adding a space at the beginning of the scanf format string - but this is a topic for another thread.)

History
Why does this post require moderator attention?
You might want to add some details to your flag.

1 comment thread

Regarding the compiler (2 comments)
Regarding the compiler
dumplings‭ wrote over 2 years ago

Oh sorry, I actually did include the #include its just that when I copied and pasted this code from my C compiler onto here, I missed it out. Maybe I'll try and see if there's any updates for my C compiler. I'm using code:blocks btw. I mean it should be fine right?

Lundin‭ wrote over 2 years ago

dumplings‭ Some versions of Codeblocks include old gcc/mingw versions before version 5.0.0. Those default to gnu90 and not to a modern C standard - they would exhibit this very bug about missing include that I mention. If you follow the advise in the link I gave, you should be able to use fairly old gcc versions though.

Skipping 1 deleted comment.