Reading out of and writing into the same file

I having a strange problem when I try and read out of a file, and then write back into it.

In one function, I'm reading it using:

Code:

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FILE *fp = fopen(args[1],r);
and then using x = fgetc

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but later on in another function I'm doing

Code:

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FILE *fp1 = fopen(args[1],w);
and then writing to it

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These file pointers are in seperate functions and neither one of them gets passed to the other function.

The problem is when I try to run it, it crashes, and the only way to solve the problem is to then change both the 'r' and 'w' to 'rw'

For some reason this then means that I can't seem to write to the file at all.

It's acting very strange, especially as the operations are done in seperate functions. It doesn't seem to like me having different file permissions from seperate pointers.

Can anyone give me any ideas as to how this sort of issue is resolved, or where I'm likely to be going wrong?

Thanks

Oh wait, just had a thought, is the reason for this possibly because I'm not closing the files using fclose() once I've finished with them?

Obviously I'd check on my code but don't have access to a compiler atm!

when u try to open the file with the write mode it clears of all the contents. And u are trying the open the file again with the read more. Which basically means u are trying to read a empty file. What u could do is u can try opening a file using "a+" mode which basically mean u open file on reading and appending condition.

ssharish2005

No I was trying to read it and then write to it(clear the previous contents)

Will have to see tomorrow if it was due to me forgetting to fclose(fp)

So is that something like u read the whole file in one fucntion ansd close that file. And agian open that file in another fucntion in write mode.

Post your code lets have a look

ssharish2005

If fopen fails, use perror(args[1]) to tell you why.

fclose()ing your file pointer might solve the problem.

You don't need two filestreams if you could use only one. Open a file in mode "r+", and rewind() the file after you've finished reading and want to start writing.

look at the function definition for fopen.

FILE *fopen(const char *FILE, const char *MODE);

the second argument to fopen is string pointer.

if you put r,w or rw the complier thinks it is a variable.

what you need to do is put "r", "w" or "a" instead. for read, write and append.

http://www.cppreference.com/stdio/fopen.html
http://opengroup.org/onlinepubs/0079...xsh/fopen.html
http://en.wikipedia.org/wiki/Fopen