Im looking for a tool that can validate if a given text\paragraph subject to a specific format .
for example :
I can be able to check if the text is as following :
xxx{
sss:aaa;
}
yyy();
preferably open source tool, with easy rule sets like xml or something .
by text i mean a string that i get from i.e fgets(), or any function that reads from a file .
For something like this I'd suggest a parser (see, for instance, What is Parse/parsing?). You can build one from a definition of the language that you want to parse using a parser generator like Yacc or its free GNU equivalent Bison, or any number of other parser generators, many of which are also freely available.
Most parsers are used to transform a text that complies with a grammar into some other form (e.g. an intermediate language or a machine code) but that isn't neccesary - in your case the parser could simply say (at a minimum) "Yes" if the text conforms to a given grammar.
Parsers for simple grammars can be built by hand but, if you have the tools available, using a parser generator is easier and more robust in my experience.
Further, the text that you've shown is similar to a portion of code written in the C language (something close to a struct declaration followed by a function call), so you would be able to re-use parts of the grammar that you need from an existing Yacc grammar for C like this one.
