Question

When running the this sample code from QFileInfo documentation:

 QFileInfo fi("/tmp/archive.tar.gz");
 QString base = fi.baseName();  // base = "archive"

Would it result in accesses to the file system?

I’m assuming that calling fi.lastModified() or fi.exists() would require the file system to be accessed, but what about it I only use it to extract parts of the file name (extension, base file name, only the directory, etc.)?

Answer 1

Without looking at the implementation of methods it is hard to say precisely which method access the filesystem and which not. But I found in the library this sort of explanation that answer your question:

Performance Issues

Some of QFileInfo‘s functions query the file
system, but for performance reasons, some functions only operate on
the file name itself. For example: To return the absolute path of a
relative file name, absolutePath() has to query the file system. The
path() function, however, can work on the file name directly, and so
it is faster.

Note: To speed up performance, QFileInfo caches
information about the file. Because files can be changed by other
users or programs, or even by other parts of the same program, there
is a function that refreshes the file information: refresh(). If you
want to switch off a QFileInfo‘s caching and force it to access the
file system every time you request information from it call
setCaching(false).