CODEWITHSUNDEEP
c++stringfile-extension
NoobScratcher
NoobScratcher

Reputation: 139

is this how i check a file extension in a specifc text file?

Hello I'm trying to implement a way too check a file extension in a specific text file the code below doesn't seem to do what I want but I was wondering if this is somewhat the right direction to take in doing this. if not what library are there that would allow me to do this in as less code as possible.

string fn = ".txt";
if(fn.substr(fn.find_last_of(".") + 1) == ".txt") {
    fprintf(stderr,"yes");
} else {
    fprintf(stderr,"no");
}

im on windows 7 32bit

Upvotes: 0

Views: 4755

Answers (4)

Samantha
Samantha

Reputation: 975

If you only need this to work on Windows, the best solution is to use the Win32 API PathMatchSpec.

For your example:

string fn = ".txt";
if(PathMatchSpecA(fn.c_str(), "*.txt") {
    fprintf(stderr,"yes");
} else {
    fprintf(stderr,"no");
}

Or as a function: 

BOOL HasTxtFileExtension(LPCSTR filename)
{
    return PathMatchSpecA(filename, "*.txt");
}

As would be expected, this function is case-insensitive and correctly handles the case where the directory contains dots but the file does not, e.g. C:\\directory.with.dots\\testtxt.

Upvotes: 1

James Kanze
James Kanze

Reputation: 153899

My preferred solution would be boost::filesystem, as minus suggests, but if not:

static std::string const targetExtension( ".txt" );
if ( filename.size() >= targetExtension.size()
        && std::equal( filename.end() - targetExtension.size(),
                       filename.end(),
                       targetExtension.begin() ) ) {
    std::cerr << "yes";
} else {
    std::cerr << "no";
}

This would seem the simplest to me.

Upvotes: 2

minus
minus

Reputation: 706

I think boost filesystem library should help you (extension path function).

http://www.boost.org/doc/libs/release/libs/filesystem/index.html

Upvotes: 0

taskinoor
taskinoor

Reputation: 46027

fn.substr(fn.find_last_of(".") + 1) returns "txt" without the dot. So either remove +1 from substr or compare with "txt" without the dot.

Upvotes: 1

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