extract from string in c using sscanf

Question

I am trying to use sscanf to extract specific values of name and msg from a string {"username":"ece","says":"hello"} as following:

sscanf(data, "{"\username"\:"\%s"\,"\says"\:"\%s"\}", name, msg);

I need 'ece' in name and 'hello' in msg but I am getting ece","says":"hello" in name and msg remains empty.

Answer 1

The %s format stops at the next white space. You need it to stop earlier, at the '"' , so you need to use a character set,

sscanf(data, "{\"username\":\"%[^\"]\",\"says\":\"%s\"}", name, msg);
                              ^^^^^^
                          read up to the next double quote

Answer 2

You need to put the escape \\ before the escaped character.

sscanf(data, "{\"username\":\"%s\",\"says\":\"%s\"}", name, msg);

And unless there is a white space after the username, all that's in the buffer will be read into name .

Use an inverse character set instead of %s, like this %[^\\"]

Answer 3

The problem is that %s conversion specification reads input until it reach whitespace character. So, you have all the data after "username" in first variable.

Answer 4

1) in the whole string format you have to correct this "\\ with \\" . The \\ to mention that that the next character is a special character and " is a special character

2) you have to replace %s with %[^\\"] for both username and says . This above regular expression means that you want to catch string which does not contain " . so the catch of the string will stop at the first "

sscanf(s, "{\"username\":\"%[^\"]\",\"says\":\"%[^\"]\"}", name, msg);