annoying validation issue with sscanf

The code below works perfectly fine with

test.txt:

blah1 44.3
blah2 34.3

as soon as i add2 blank lines to the end of the text file

else kicks in:

Number of lines: 1
Number of lines: 2
line cannot be printed

Is it possible, once the end of the file is reached to exit somehow and ignore how many blank lines there are at the end?

[code]

#include <stdio.h>
#include <stdlib.h>

int main()
{
FILE *fp;
char name[25];
char buff[BUFSIZ];
float num;
int nooflines = 0;

if((fp=fopen("test.txt","r"))==NULL)
{
perror("File cannot be opened");
exit(1);
}

while(fgets(buff,sizeof(buff),fp)!=NULL) // read a single line from the file till i get EOF
{
if(sscanf(buff,"%s %f",name,&num)==2) // getting the name and the number from the buffer which was read from the file
{
nooflines++;
printf("%s %d", "\n Number of lines: ", nooflines);
}
else
{
printf("\nline cannot be printed\n");
exit(0);
}
}

return 0;
}

I've tried modifying the if statement to:

Code:

if(sscanf(buff,"%s %f",name,&num) == 2 || sscanf(buff,"%s %f",name,&num) != '\n' )

it works

but if i add crap to the
text file:

blah1 44.3
dsds
blah2 34.3

it still reads it as a valid line (i.e. the second line in the text file is not valid it has no valid number). I tried changing the || to && but it gives me the same original problem i had.

Sure, just use something like

Code:

if(!buff[0] || (!buff[1] && buff[1] == '\n')) continue;

which will skip over blank lines (blank except for a new line).

Is that what you meant?

i did something simliar:

Code:

if(sscanf(buff,"%s %f",name,&num) != '\n' )

it just prints out

Number of lines: 1
Number of lines: 2
Number of lines: 3
Number of lines: 4

it doesn't seem to skip the blank lines i added 2 lines of text and 2 blank lines

Comparing the return value of sscanf to '\n' doesn't make much sence.

Quote:

Return Value.
The number of items succesfully read. This count doesn't include any ignored fields.
If EOF is returned an error has occurred before the first assignation could be done.

hmm you have a point there.

i got it to work:

Code:

while(fgets(buff,sizeof(buff),fp)!=NULL) // read a single line from the file till i get EOF { if(sscanf(buff,"%s %f",name,&num) != '\n' && sscanf(buff,"%s %f",name,&num) == 2 ) // getting the name and the number from the buffer which was read from the file { if(!buff[i] || (!buff[i] && buff[i] == '\n')) continue; nooflines++; printf("%s %d", "\n Number of lines: ", nooflines); i++; } else { printf("\nline cannot be printed\n"); exit(0); } }

one prob though, for some reason "line cannot be printed even though i have no blank lines etc.

Code:

sscanf(buff,"%s %f",name,&num) != '\n'

Fix that!

whoops, i actually tried it without that bit but it still prints out "cannot be printed" i have the correct format for sscanf.

Code:

while(fgets(buff,sizeof(buff),fp)!=NULL) // read a single line from the file till i get EOF { if(!buff[i] || (!buff[i] && buff[i] == '\n')) continue; if(sscanf(buff,"%s %f",name,&num) == 2 ) // getting the name and the number from the buffer which was read from the file { nooflines++; printf("%s %d", "\n Number of lines: ", nooflines); i++; } else { printf("\nline cannot be printed\n"); exit(0); } }

Works for me with a test.txt file that contains string<space>floating point<newline> lines, what is your input?

blah1 44.3
blah1 44.3

there's two blank lines at the bottom

Number of lines: 1
Number of lines: 2
line cannot be printed <- shouldn't be there :|

Why shouldn't it?

You are reading in each line, and you are using fscanf to read in a string and a double. Of course it's going to fail (not return 2) if you feed it a blank line instead of a string/double pair.

What is it you actually expect to happen? If you want to ignore blank lines, check if the fgets result string only contains a newline, then skip your fscanf if that is the case.

Yes, instad of it printing 'there's an error' i just want it to ignore empty lines are print nothing.

i know what you mean with changing the fgets line, but i cant get it to compile 'operands of != have illegal types 'pointer to char' and 'char'

Code:

while(fgets(buff,sizeof(buff),fp)!=NULL && fgets(buff,sizeof(buff),fp)!='\n') // read a single line from the file till i get EOF { if(sscanf(buff,"%s %f",name,&num) == 2) // getting the name and the number from the buffer which was read from the file { if(!buff[i] || (!buff[i] && buff[i] == '\n')) continue; nooflines++; printf("%s %d", "\n Number of lines: ", nooflines); i++; } else { printf("\nline cannot be printed\n"); exit(0); } }

Comparing the return value of fgets to '\n' is ridiculous. fgets returns a pointer, either NULL or the pointer passed. The only thing you should be comparing to '\n' is buff[0], ie the first character of the result string.

And you should do this BEFORE, not after the sscanf, because you want to continue to the next line without reading it with sscanf.

you mean?

Code:

while(fgets(buff,sizeof(buff),fp)!=NULL) // read a single line from the file till i get EOF { if(!buff[i] || (!buff[i] && buff[i] == '\n')) continue; if(sscanf(buff,"%s %f",name,&num) == 2) { nooflines++; printf("%s %d", "\n Number of lines: ", nooflines); } else { printf("\nline cannot be printed\n"); exit(0); } i++; }

Number of lines: 1
Number of lines: 2
line cannot be printed

No.

Code:

if(!buff[i] || (!buff[i] && buff[i] == '\n')) continue;

what on earth is that supposed to do? For a start, what is i? It makes no sense at all, and will always be false anyway. Why not just do:

Code:

if (buff[0] == '\n') continue;

Simple.

ahh so you actually meant buff[0] sorry, i misunderstood. I thought i had to increment the line as i work through the file. thanks.

Yes, when I said "buff[0]", I meant "buff[0]". :p

buff is a char array, so buff[0] is the start of the line after fgets. buff[1] is the second character, until buff[something] is '\0', indicating the end of the string.

You are reading each line into the same char array, buff, so buff[0] is always the first character of each line after the fgets.