The man page for sscanf on my machine indicates that [ "matches a
nonempty sequence of characters", so failing to match an empty
character sequence seems to be correct behavior.
On Mon, Jul 15, 2024 at 10:16 PM U.Mutlu <u...@mutluit.com> wrote:
>
> The below test code demonstrates that sscanf fails
> to parse the string "" (ie. an empty string inside "") in line2 (fErr=1).
> Is this a bug?
> Or is there maybe a workaround format string to be used with sscanf ?
>
> /*
> sscanf_bug_demo.cpp
>
> sscanf fails scanning the string ""
>
> Compile:
> g++ -g -Wall -Wextra -std=c++11 sscanf_bug_demo.cpp
>
> Run:
> ./a.out
>
> Input lines:
> joe "prj 1" "blah foo"
> jim "" "quantum leap"
>
> Output:
> line1: n=3 : fErr=0 : un="joe" prj="prj 1" desc="blah foo"
> line2: n=1 : fErr=1 : un="jim" prj="" desc=""
> */
>
> #include <cstdio>
> // using namespace std;
>
> void sscanf_bug_demo()
> { // sscanf fails scanning the string ""
>
> // test data:
> // line format: username "prj" "desc" (the string in "" can be empty)
> const char* line1 = "joe \"prj 1\" \"blah foo\"";
> const char* line2 = "jim \"\" \"quantum leap\"";
>
> char un[32], prj[16], desc[256];
> int n;
> bool fErr;
>
> // parsing via sscanf:
>
> un[0] = 0, prj[0] = 0, desc[0] = 0; // clear them before filling
> n = sscanf(line1, "%31[^ ] \"%15[^\"]\" \"%255[^\"]\"", un, prj, desc);
> fErr = n < 3;
> printf("line1: n=%d : fErr=%d : un=\"%s\" prj=\"%s\" desc=\"%s\"\n",
> n, fErr, un, prj, desc);
>
> un[0] = 0, prj[0] = 0, desc[0] = 0; // clear them before filling
> n = sscanf(line2, "%31[^ ] \"%15[^\"]\" \"%255[^\"]\"", un, prj, desc);
> fErr = n < 3;
> printf("line2: n=%d : fErr=%d : un=\"%s\" prj=\"%s\" desc=\"%s\"\n",
> n, fErr, un, prj, desc);
> }
>
> int main()
> {
> sscanf_bug_demo();
> return 0;
> }
>
