Oops what does this mean in c?

Question

if ( sscanf( line, "%[^ ] %[^ ] %[^ ]", method, url, protocol ) != 3 )...

That format above is very strange,what's it doing?

Answer 1

That line is attempting to read 3 strings that do not contain a space separated by spaces into method, url, protocol and if it fails to read 3 it will then enter the if block.

Answer 2

the [] is the scanset. If you tell %[abcd] then an input string only with a or b or c or d will be considered. The string would terminate at the first occurance of some other character which is not any of the characters in the braces.

The ^ inside the [] is used to denote the compliment of the set inside the braces. Like with the format string %[^abcd] will only accept all characters except , a or b or c or d.

so in %[^ ] , the blankspace followed by the ^ tells that, the format string will accept any character combination in the string which does not have a blankspace.

The format string "%[^ ] %[^ ] %[^ ]" will match a string which has three components separated by blankspaces. Each of the component will contain a sequence of characters which have no space inside them.

The function returns the number of input items successfully matched and assigned, which can be fewer than provided for, or even zero in the event of an early matching failure.

So the above function will return 3 only if and only if all the three components are read, that is, the input line has three partitions and for each partition the three arrays method, url and protocol was populated.