Shaji Kalidasan wrote:
You can use more than one file test on the same file to create a complex logical condition. Suppose you only want to operate on files that are both readable and writable; you check each attribute and combine them with and: if (-r $file and -w $file) { ... } Each time you perform a file test
or use stat() or lstat()
, Perl asks the filesystem for all of the information about the file (Perl’s actually doing a stat each time, which we talk about in the next section). Although you already got that information when you tested -r, Perl asks for the same information again so it can test -w. What a waste! This can be a significant performance problem if you’re testing many attributes on many files. The virtual filehandle _ (just the underscore) uses the information from the last file lookup that a file test operator
or stat() or lstat()
performed. Perl only has to look up the file information once now:
John -- Any intelligent fool can make things bigger and more complex... It takes a touch of genius - and a lot of courage to move in the opposite direction. -- Albert Einstein -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/