fseek on different editors

Hi,
I am designing a parser in which I am using fseek to go back in a file.
The problem that I am facing is that if the file opened is written in a notepad, then it works file. But if the file is written in some other editor,on using fseek, the file pointer moves to some other unintended position and causes the logic to fail.
(It works fine on a single character but fails when I pass string length as a parameter))

eg.
long int vl_strlen = strlen("abcd");

fseek(fp,vl_strlen,SEEK_CUR);

Is there any solution to this problem ?

fp must point to the undefined area.I suggest you use the whence "SEEK_SET" which is easy to control.

I am parsing a file with 1000 odd lines.
If I have to to go back lets say, one word back from the current position, I can't use SEEK_SET in this case as it starts from the beginning of the file.
And also it happens in between, so there is no chance of pointing to an undefined area..

For what popurse you use the fseek(), you want to return the location or the number of characters?

For streams opened in text mode, fseek has limited use, because carriage return–linefeed translations can cause fseek to produce unexpected results. The only fseek operations guaranteed to work on streams opened in text mode are:

From MSDN.

Good catch, Bayint Naung

Yeah, we don't know how in which mode the file was opened. Perhaps the Ctrl-Z's occurring in files other than simple text files are interpreted as end-of-file indicators.

Perhaps the text file came from another system where the end-of-line characters either include or don't include LF. Or is it CR. It's been so long ago. That's always been a transportability issue.

No. You can't store EOF in a char. The reason it isn't reliable on "text mode" (which may not actually be different than "binary mode") is the NL / CR issue. Some use one, some use the other, some use both.


Quzah.

Can't you simply 'look ahead' say one token?

Originally Posted by Bayint Naung

Can't you simply 'look ahead' say one token?

fgetc + ungetc


Quzah.

Thanks guys...
the problem was of CR LF only...
opening the file in binary mode has solved the issue...

Originally Posted by quzah

fgetc + ungetc


Quzah.

Not so sophisticated. Only 1 char push back ?

Yes, you can only unget one character. I'm too tired to put it in the right words, but you're only ever allowed to unget the latest thing. If you've read two items, only the last one can be put back, and once you've used unget, you can't use it again without first reading something from the stream. (I.e., you can only unget the last thing read.)

Quzah.