Usually returned if the end of the input stream is reached or if a read error occurs before any conversion.
Always verify your FILE * pointer immediately after fopen . Defensive programming is the only way to prevent a null stream from breaking your application.
To write robust code, always treat the file pointer as a conditional gatekeeper: Fscanf C Expression Stream Null
If the stream is NULL , fscanf doesn't return EOF ; it crashes. You must check the stream before it becomes part of the fscanf expression. 4. Best Practices for Stream Safety
In C, fscanf is an expression that evaluates to an int . Understanding this value is critical for handling streams safely: Usually returned if the end of the input
Are you trying to debug a or segment of code right now?
FILE *fptr = fopen("non_existent_file.txt", "r"); // If the file didn't open, fptr is NULL. // The next line will crash the program: fscanf(fptr, "%s", buffer); Use code with caution. Copied to clipboard 3. The "Expression" and Return Value To write robust code, always treat the file
Most developers don't pass NULL on purpose. It usually happens because of a failed fopen call: