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How does fread work?
The fread() function returns the number of full items successfully read, which can be less than count if an error occurs, or if the end-of-file is met before reaching count. If size or count is 0, the fread() function returns zero, and the contents of the array and the state of the stream remain unchanged.
Does fread update the file pointer?
4 Answers. Answer: Yes, the position of the file pointer is updated automatically after the read operation, so that successive fread() functions read successive file records.
How do you know if fread fails?
If fread returns fewer than the requested number of records, you’ve either hit EOF or a serious read error. You can distinguish between them by checking feof() and ferror() . Similarly, if fwrite returns fewer than the requested number of records, you’ve either run out of disk space or hit a serious write error.
What is the output of fread?
The fread() function will keep returning 1 until there are records in the file. As soon as the end of the file is encountered fread() will return a value less than 1 and the condition in the while loop become false and the control comes out of the while loop. In line 33, fclose() function is used to close the file.
Does fread read null terminator?
Will fread() read the null terminated string? Absolutely, fread() just reads data out of the file as bytes. But, you can’t ask it to read the next null-terminated string, because it doesn’t know or care about strings.
How does Fread work when file size is less than 1000 bytes?
The former returns the actual number of bytes read. The latter returns 0 if the file size is less than 1000, otherwise it returns 1. In both cases the buffer would be filled with the same data, i.e. the contents of the file up to 1000 bytes.
When to use FREAD to read in smaller chunks?
Read in smaller chunks if partial reads are useful. According to the specification, the two may be treated differently by the implementation. If your file is less than 1000 bytes, fread (a, 1, 1000, stdin) (read 1000 elements of 1 byte each) will still copy all the bytes until EOF.
When to use 0 or 1 in FREAD?
The latter returns 0 if the file size is less than 1000, otherwise it returns 1. In both cases the buffer would be filled with the same data, i.e. the contents of the file up to 1000 bytes. In general, you probably want to keep the 2nd parameter (size) set to 1 such that you get the number of bytes read.
How does the result of fread really work?
On the other hand, the result of fread (a, 1000, 1, stdin) (read 1 1000-byte element) stored in a is unspecified, because there is not enough data to finish reading the ‘first’ (and only) 1000 byte element. Of course, some implementations may still copy the ‘partial’ element into as many bytes as needed. That would be implementation detail.