sugarfree

Hi everyone,

Imagine that I have a file with the following content

string 'string' string' <continues with more text>

string here is only A-Z and a-z characters.

I only want to get string or 'string', is this possible with fscanf?

I came up with:

The last fgets is for non string characters. The code above output string 'string' string'

My other doubt is about fgets, I'm a bit unsure if I really need it, but if I just wanted the string, doing fscanf(fp,"%[A-Za-z]",buf); would block on the white space.

Thanks for the all the input.

MK27

What you may want to consider is reading in all the data with fgets() first, then extract the parts you want using sscanf() instead of fscanf(). sscanf() reads from a char pointer instead of a file stream.

If the file has more that one line, you can do this in a loop with a one line buffer for fgets.

__________________
C programming resources:
GNU C Function and Macro Index -- glibc reference manual
The C Book -- nice online learner guide
Current ISO draft standard
CCAN -- new CPAN like open source library repository
GDB tutorial #1 -- gnu debugger tutorials -- GDB tutorial #2
cpwiki -- our wiki on sourceforge

sugarfree

Extracting information with sscanf isn't the same as extracting with fscanf? I believe they work in a similar manner.

Anyway, I found out that using fscanf like I did, it can overflow. I have to be more careful.

brewbuck

They do, but by using fgets() followed by sscanf() you get much more control over how the individual lines of input are handled. The *scanf() family of functions treats all whitespace as the same, including end-of-line markers, which leads to a well-known set of issues that people constantly ask about here.

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MK27

Ditto what brewbuck said.

Which is one reason it's good to use fgets then sscanf(). Altho you can actually prevent overflow with *scanf() functions too:
will read a maximum of 31 bytes. But then the rest is left in the input buffer. If instead you just use a large buffer with fgets (say 4096 for a line, since that's actually several pages), you can more easily dispose of the unwanted data and continue on.

__________________
C programming resources:
GNU C Function and Macro Index -- glibc reference manual
The C Book -- nice online learner guide
Current ISO draft standard
CCAN -- new CPAN like open source library repository
GDB tutorial #1 -- gnu debugger tutorials -- GDB tutorial #2
cpwiki -- our wiki on sourceforge