An issue with using fscanf_s to read data like "&1&2" from a file.

**qingxing2005** · 05-28-2008

Dear all,

I met a problem about using "fscanf_s" to read string "&1&2" from the file "A.txt". The snippet of the code is described as follows,

char first[5];
char second[5];
int number1 = 0;
int number2 = 0;

err = fopen_s(&fp_t, "c://A.txt", "r");

fscanf_s(fp_t, "%s%d%s%d", first, number1, second, number2);

While the problem is after the above "fscanf_s" is executed, the values of first, number1, second, number2 are not changed, by which means the program fails in reading data. The ideal result should be first[0] = "&", second[0] = "&", number1 = 1, number2 = 2.

Thereby, can you help me a little bit?

Thanks in advance,

Bests,

Qing

**Elysia** · 05-28-2008

It reads all the "&1&2" as a string.
You'll want to read a character, to force it to read only one char.
I'd also like to give you a link: http://cboard.cprogramming.com/showp...37&postcount=9

**matsp** · 05-28-2008

Code:

err = fopen_s(&fp_t, "c:\A.txt", "r");

will most likely fail to open the file in the ROOT of C:. If you use "a.txt" it would fail to open the file at all, since it would translate \a into CTRL-G ('\07'), and that's not a valid filename.

Use double back-slashes when specifying filenames (or anything else in a C-style string constant).

--
Mats

**vart** · 05-28-2008

%s reads upto whitespace, not upto digit
something like
%[^0-9] - should read string till the digit encountered

also note that scanf needs pointers to int to modify its values...

**qingxing2005** · 05-29-2008

Dear all,

thanks for all of you guys' replies.

For the URL of file, it was my mistake to specify it wrongly. In the real code, the URL is stored in a string, which should follow the right patter, say "//". I changed it already

For the right solution, as Elysia pointed out, I gotta read the characters one by one.

thanks,

Qing.

Originally Posted by matsp

Code:

err = fopen_s(&fp_t, "c:\A.txt", "r");

will most likely fail to open the file in the ROOT of C:. If you use "a.txt" it would fail to open the file at all, since it would translate \a into CTRL-G ('\07'), and that's not a valid filename.

Use double back-slashes when specifying filenames (or anything else in a C-style string constant).

--
Mats

**Elysia** · 05-29-2008

Just pointing out, but a local filename is not an URL.
"http://blablabla.com" <-- this is an URL
"C:\test.txt" <-- this is a filename.

**robwhit** · 05-29-2008

> err = fopen_s(&fp_t, "c://A.txt", "r");

And this is neither a filename or a URL.

Well, maybe because fopen accepts /s and \s under windows, but two /s would be redundant.

**Elysia** · 05-29-2008

Some functions will accept "C:\\A.txt" (which mostly like "C://A.txt" will be translated to), but others do not, so it isn't safe to rely on it. Only one backslash in Windows filenames.

**matsp** · 05-29-2008

Originally Posted by Elysia

Some functions will accept "C:\\A.txt" (which mostly like "C://A.txt" will be translated to), but others do not, so it isn't safe to rely on it. Only one backslash in Windows filenames.

No, you need two backslashes in quoted strings, because one disappears (and depending on the next character(s), it may remove/translate the following character(s) to something you didn't want). If you use forwards slashes, which, as stated, many Windows C libraries will support, then you should use just one.

--
Mats

**Elysia** · 05-29-2008

Yes, I know, I was mentioning real string and not C-strings.
Two backslahes is not always a valid filename.

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