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Asked: 2026-06-11T14:10:12+00:00

Good day, I tried parsing this query string: pkname=Paras&key=password123 with this code: printf(Content-type:text/html\n\n); printf(<html><body>);

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Good day, I tried parsing this query string:

pkname=Paras&key=password123

with this code:

printf("Content-type:text/html\n\n");

printf("<html><body>"); 

data = getenv("QUERY_STRING");

if(data){
    sscanf(data, "pkname=%10[^&]&key=%30[^&]&", pkname, key);

    printf("%s", pkname);
    printf("%s", key);

}

printf("</html></body>");

But i can’t seem to get the key right, since the its output is always null:

Paras(null)
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1 Answer

  1. Editorial Team

    You don’t show the definition of the variable key but the fact that it prints out as (null) strongly suggests that its value is NULL, and that both printf and sscanf are trying to protect you by not segfaulting on NULL pointers. (The GNU libc implementations do that; printf prints NULL as (null) and sscanf appears to just stop parsing.)

    What you probably wanted was something like:

    char pkname[11];
char key[31];

    although you might also find the m qualifier useful, since it avoids the need to specify arbitrary field length limits.

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