Perl Tricks and Tips
Always begin all scripts with:
use warnings; # All scripts should use warnings!
use strict; # insist on good programming
End scripts (so that the window doesn't immediately close) with:
Comments are indicated with #
Identifiers starting with $ are variables (of any type!)
Identifiers starting with @ are arrays, but individual elements are accessed like $myarray.
unlink is "delete". Thus:
unlink "example.txt"; # will delete the file example.txt
Files can be copied using the module "File::copy":
Many operators can be used with files (or directories) using the syntax:
Where the operator is one of these:
-r File is readable by effective uid/gid.
-w File is writable by effective uid/gid.
-x File is executable by effective uid/gid.
-o File is owned by effective uid.
-R File is readable by real uid/gid.
-W File is writable by real uid/gid.
-X File is executable by real uid/gid.
-O File is owned by real uid.
-e File exists.
-z File has zero size (is empty).
-s File has nonzero size (returns size in bytes).
-f File is a plain file.
-d File is a directory.
-l File is a symbolic link.
-p File is a named pipe (FIFO), or Filehandle is a pipe.
-S File is a socket.
-b File is a block special file.
-c File is a character special file.
-t Filehandle is opened to a tty.
-u File has setuid bit set.
-g File has setgid bit set.
-k File has sticky bit set.
-T File is an ASCII text file (heuristic guess).
-B File is a "binary" file (opposite of -T).
-M Script start time minus file modification time, in days.
-A Same for access time.
-C Same for inode change time (Unix, may differ for other platforms)
Thus " if ( -e $filename ) " will test to see if a file exists.