Learning Perl on Win32 Systems

Globbing

The command prompt usually takes a solitary asterisk (*) command-line argument and turns it into a list of all of the filenames in the current directory. So, when you say del *, you’ll remove all of the files from the current directory. (Don’t try this unless you like restoring the current directory from your backup device.) Similarly, *.c as a command-line argument turns into a list of all filenames in the current directory that end in .c, and c:\temp\backup* is a list of all filenames in the directory c:\temp that begin with backup. (If this information is new to you, you probably want to read some more about using the command line somewhere else before proceeding.)

The expansion of arguments like * or *.c into the list of matching filenames is called globbing. Perl supports globbing through a very simple mechanism—just put the globbing pattern between angle brackets or use the more mnemonically named glob function, like this:

@a = <*.plx>;
@a = glob("*.plx");

In a list context, as demonstrated here, the glob returns a list of all names that match the pattern or an empty list if none match. In a scalar context, the next name that matches is returned, or undef is returned if there are no more matches; this process is very similar to reading from a filehandle. For example, to look at one name at a time:

while (defined($nextname = <c:/scripts/*.plx>)) {
		print "one of the files is $nextname\n";
}

Here the returned filenames begin with c:\scripts\, so that if you want just the ...