Function fread not terminating string by \0

Question

New to files in C, trying to read a file via fread

Here's the content of the file:

line1 how

Code used:

char c[6];
fread(c,1,5,f1)

When outputting var 'c', the contents appear with a random character at the end (eg: line1*)

Does fread not terminate the string or am I missing something?

Equitation

fread only reads bytes into buffers. it knows nothing of what you call a string. – Negron

Answer 1

No. The fread function simply reads a number of elements, it has no notion of "strings".

• You can add the NUL terminator yourself
• You can use fgets / fscanf instead

Personally I would go with fgets.

Glindaglinka

for those interested, an example implementation to remove newline from fgets is given here: #2694276 – Fourteenth

Answer 2

Sorry i'm a little late to the party.

No, fread doesn't handle this for you. It must be done manually. Luckily its not hard. I like to use fread()'s return to set the NUL like so:

char buffer[16+1]; /*leaving room for '\0' */
x = fread(buffer, sizeof(char), 16, stream);
buffer[x]='\0';

and now you have yourself a \0 terminated string, and as a bonus, we have a nifty variable x, which actually saves us the trouble of running strlen() if we ever needed it later. neat!

Belgium

Answer 3

The man page for fread says nothing about adding a terminating zero at the end of the file.

If you want to be safe, initialize all the bytes in your c array to be zero (via bzero or something like that) and when you read in, you'll then have a terminating null.

I've linked the two man pages for fread and bzero and I hope that helps you out.

Aylmar

bzero() is deprecated (and has been removed from POSIX.1-2008) in favour of memset(). – Caelian