_learning perl_, ch13, 11.I.2002, nh

FILE AND DIRECTORY MANIPULATION

removing a file
~~~~~~~~~~~~~~~
  `unlink` -- removes a file
    |
    `->  unlink("fred.txt",$file); # removes fred.txt
         unlink<*.txt>             # removes all .txt files (glob
                                     evaluated in a list context)
  
  * just like unix `rm`
  * can take a series of names 
  * can take variable names
  * return value is number of files successfully deleted
    -- but can't tell which of many, if one fails:

    for (<*.txt>){   # step through each file, using $_
      unlink || warn "having trouble deleting $file: $!\n";
    }


renaming a file
~~~~~~~~~~~~~~~
  `rename` -- renames a file
    |
    `-> takes two arguments -- old, new
        rename("fred","barney") || die "can't rename: $!\n";

  * just like unix `mv`
  * but can't just stick it in new directory magically like mv:
      rename("file","some-directory/file");   # must specify name
  * _doesn't_ copy if moved from one mounted device to another


linking
~~~~~~~
           /--> hard links
  es gibt *
           \--> soft links (=~ symbolic links; symlinks)

    hard links
    ----------
      - virtually identical to file
      - must be on same mounted filesystem
      - restricted for directories -- one from root, its own ./, and
        ../s from its subdirectories

    symbolic links
    --------------
      - contains a pathname as data
      - contents of a symlink do not have to refer to an existing
        file or directory!
      - can point off the current filesystem, onto another mounted
        one

    creating hard & sort links with perl
    ====================================
      hard: `ln` in shell
            `link` in perl:
              link("fred","maincharacter") || die "dying! $!\n";
             |
             `-> as with rename, must specify full path

      soft: `ln -s` in shell
            `symlink` in perl:
              symlink("barney","neighbor") || die "can't!: $!\n";

            `readlink` tells where a link points
             ^^^^^^^^

making & removing directories
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  `mkdir` 
   ^^^^^
    |
    `-> takes name of directory and permissions:
          mkdir("foo",0777) || die "can't mkdir foo: $!\n";

  `rmdir`
   ^^^^^
    |
    `-> takes directory name
          rmdir("foo") || die "can't remove dir foo: $!\n";

other modfying commands:
~~~~~~~~~~~~~~~~~~~~~~~
  * chmod(0666,"filename");  # -rw-rw-rw- filename
  
  * chown -- takes a UID, a GID, & a list of filenames
          -- is like `chown` AND `chgrp`
  
  * utime -- measured in seconds since January 1, 1970
          -- takes