Skilled Unix users know the importance of the shell or command line interface (CLI). (Old-time Unix users didn't even have a choice about it). While having more of a learning curve than a graphical user interface (GUI), it permits powerful, creative, complex operations to be specified quickly and reliably. For anyone but the superficial user, learning a CLI is an investment that pays off rewardingly. Command line environments are still readily usable over low-bandwidth network connections and restricted displays. Neal Stephenson explains the history and values of computer interfaces exceedingly well in "In the Beginning was the Command Line" <https://en.wikipedia.org/wiki/In_the_Beginning..._Was_the_Command_Line>. One can even build a strong case that a CLI is best for a learning new computer user, as described in "The Command Line - The Best Newbie Interface?" <https://osnews.com/story.php?news_id=6282>.

However, when one is concerned about file manipulation and management (which is a very good thing to be concerned about as the basis of your interface, as most GUIs would rather lead you to forget), a CLI can be a frustratingly terse interface to the filesystem. Too many tedious ls(1) and cd(1) commands are needed to keep watch on what's there. A GUI file manager can address this problem, but then you're in mouseland and have lost the advantages of the CLI.

Enter the visual shells. Not a new idea, visual shells can operate within an entire terminal or console screen. File listings are displayed for your constant reference. Common commands and operations can typically be performed in fewer keystrokes in a visual interface. As the vi(1) visual editor evolved from the ed(1) and ex(1) command line editors, visual shells have attempted to evolve from command line shells. Some visual shells have promoted themselves as simpler menu-oriented interfaces suitable for novices, while others emphasize more expert functionality.

Nonetheless, visual shells have never really caught on, except some in certain circles such as Emacs' "dired" mode and the Midnight Commander program. I believe this is because they have been designed as largely self-contained applications with limited configurability. Using a visual shell has required a significant jump into a new base interface tool, and few are so compelling or standard to make that worthwhile.

Hence the design of vshnu, the New Visual Shell. In the Unix tradition, it works with things already there and fills a empty niche. When incorporating it into your Unix environment, you keep your command line shell, your editor, your pager, and access to all your tools, tricks and know-how. Vshnu can operate as an optional supplemental visual mode to your command line shell. You switch between command line and visual mode easily as you wish. Your interface bandwidth and power for Unix operations is on a higher plane and life gets sweeter. In addition, being written in Perl, it ports to any Unix system without compilation, gives you the advantages of a Perl interpreter running readily at hand, and permits visual command customizability limited only by your creativity, yet doesn't require knowledge of Perl for normal usage. Vshnu is a tool that's worthwhile even if only used occasionally as an interactive, pageable, color ls(1), yet still pays back, with interest, whatever more you put into using it.

• Extensive options for sorting and listing a directory's files
• Multiple methods for navigating directories and selecting files
• Directory locations may be marked for quick returns
• Lists colored command outputs alongside files, including a builtin "ls -l" and "df"
• Directory and file histories
• In color terminals, uses color for more informative displays, including file coloring by type via the standard LS_COLORS environment variable
• Expands and collapses chosen subdirectories

• Multiple methods for choosing and operating on individual or arbitrary sets of files
• Key commands and file actions are 100% configurable, extensible, self-documenting and arbitrarily complex, including multiple choice options
• File actions are customizable by file name/type/contents/etc, with common actions configured by default
• Online help descriptions of key commands and file actions, by mode and by command
• Separate per-site and per-user configurability

• Adjustable file column displays
• Adapts to changing screen sizes (but works best on screens 80 characters wide or more)
• Current directory and environment is propogated between vshnu and the parent command line shell
• Multiple interfaces for shell commands and Perl statements
• Perl statements may be {{embedded}} within shell commands
• A Perl "where" clause to subset the displayed files

• Many actions available via the mouse in terminals with xterm(1)-like mouse support
• Can use mailcap(4) files for specifying file actions by MIME type
• Can use the CD_PATH environment variable as a search path for files and directories
• Recognizes the following standard environment variables: ANSI_COLORS_DISABLED, DISPLAY, EDITOR, HOME, HOST, LS_COLORS, MAIL, MAILCAPS, MAILER, PAGER, PATH, PERL_RL, SHELL, TERM and VISUAL

Vshnu was inspired by and initially patterned after the program vsh, the Visual Shell <https://kinzler.com/me/vshnu/vsh.txt> <https://kinzler.com/me/vshnu/vsh-4.2k.tgz>. Vsh was written in the early 1980's and is pretty much obsolete bit rot now. After failing to be included in a BSD distribution, it faded into obscurity. A SunOS port hasn't compiled since the pre-Solaris days, and an attempted Linux port is still horrendously buggy. But, it started with some right ideas. I used vsh almost my entire Unix career before finally writing vshnu to replace, extend and modernize it.

The "nu" in "vshnu" implies "new", of course, as well as invokes the Hindu god Vishnu, the preserver of the universe and restorer of dharma (moral order). Hmmm, how appropriate.

1. PREREQUISITES

   You need Perl 5.002 or greater with the Term::Screen and Term::ANSIColor modules -- all available at <https://www.cpan.org>. Term::Screen and Term::ANSIColor module files are also included here in the libperl/Term directory. If you wish to install these, just add a ".pm" extension to the filenames and copy them into a directory in your Perl's @INC or into $HOME/perl/Term, $HOME/lib/Term or $HOME/lib/perl/Term.

   Term::Screen uses Term::Cap, so you'll need a termcap file containing your terminals' capabilities definitions. Most systems already have one, but in case yours doesn't, a brief one containing only some common terminals is at <https://kinzler.com/me/home.html#etc/termcap>. The termcap file may be installed as $TERMCAP, $HOME/.termcap, /etc/termcap or /usr/share/misc/termcap. Or on (older) Debian systems, you can just run `apt-get install termcap-compat`.

2. OPTIONAL

   The Term::ReadLine::Gnu, or at least the Term::ReadLine::Perl, module is recommended to provide line editing, history, filename completion, and insertions (with M-v) within vshnu <https://www.cpan.org>. Other modules that Perl can use, if installed, for particular features are Data::Dumper, Filesys::DiskFree, MIME::Types and Mail::Cap.

   If available, vshnu can make good use of color in a terminal or console with ANSI color support, and this is highly recommended. For X Windows, the latest versions of xterm(1) and urxvt(1) have proper color support. Make sure your termcap information is properly defined for your color terminal. You'll then also want the GNU fileutils software <https://www.gnu.org/software/fileutils/> which includes the dircolors(1) tool for setting your LS_COLORS environment variable. This variable is referenced by GNU ls(1) and vshnu to determine how files should be colored by type and name. As an example, the file color specification file I use is available at <https://kinzler.com/me/home.html#etc/colorrc-ansi> .

   A terminal with xterm(1)-like mouse support will enable the use of vshnu's mouse functionality.

   The xcb(1) utility will be required for the interfaces to the X11 cut buffer to work <http://software.schmorp.de/pkg/xcb.html>.

3. INSTALLATION

   Vshnu may be installed either as a regular Perl module or manually in any desired locations, including your home directory.

   1. AS A PERL MODULE

      The usual routine

      perl Makefile.PL
      make install clean

      should properly install the "vshnu" file in your Perl scripts directory and the "vshnucfg.pl" file in your Perl library directory.

   2. MANUALLY

      You can edit the first line of the "vshnu" script here to contain the proper path to your perl executable, then copy it into any directory in your PATH. Make sure the copy's made executable.

      Then the "vshnucfg.pl" file can be copied where you wish. If it's not installed as $HOME/.vshnucfg or as vshnucfg.pl somewhere in your Perl's @INC or in $HOME/perl, $HOME/lib or $HOME/lib/perl, then you'll have to set the VSHNUCFG environment variable to its location, or edit the installed "vshnu" script near the top to set $default_vshnucfg.

4. SHELL INTEGRATION

   Optionally, your regular shell environment can be enhanced to interact with vshnu as a sort of supplemental visual mode, communicating any environment changes to vshnu and directory changes between the two shells.

   See the subdirectory here for your command line shell for further direction. Contributions of other shell integrations are very welcome.

5. PERSONAL CONFIGURATION

   The installation procedure described above installs the main vshnu "engine" script and the supplied required configuration file. An entirely new configuration file could be written and substituted for the supplied one for a vshnu with a very different key command structure and operation (modeless perhaps). Contributions of additions or improvements to the vshnucfg file are welcome.

   Usually, though, you'll just want to add on some personal extras or tweak a few things in the supplied configuration. This can be done with a "vshnurc" Perl file. It's loaded after the "vshnucfg" Perl file (installed above) and so can modify or supplement the effects of anything in it. Both of these files are just Perl code that define operating structures for vshnu's environment. The location of the vshnurc file is assumed to be $HOME/.vshnurc (or vshnurc.pl in Perl's @INC or in $HOME/perl, $HOME/lib or $HOME/lib/perl) unless the VSHNURC environment variable is set (or the $default_vshnurc variable is set in the vshnucfg file). My personal vshnurc file is included here as "vshnurc.pl" as an example to start your own. Some familiarity with Perl will probably be required to do any significant work within these files.

   If the Mail::Cap, and perhaps MIME::Types, modules are available, vshnu's supplied configuration will use any mailcap(4) files it finds (in $MAILCAPS or $HOME/.mailcap, /etc/mailcap, /usr/etc/mailcap and /usr/local/etc/mailcap) for offered file actions for any file types it doesn't otherwise cover. Also, it will recognize a vshnu-specific mailcap file (in $VSHNUCAP or $HOME/.vshnucap or the $default_vshnucap variable set in the vshnucfg file) for file actions to supersede its usual configuration. For example, if you prefer xv(1) over display(1) for viewing image files, you may find adding this line to your vshnucap file simpler than changing your vshnurc file:

   image/*; xv %s; dontneedterminal

This is the minimum you'll want to know to make some good use of vshnu with the supplied configuration:

Upon starting vshnu, you should see a listing of the files in your current directory. You can enter a subdirectory by typing the letter that labels it. Typing the label letter of a file will load that file into your editor. You can go up to the parent directory with <Return> or back to the previous directory with '\'. With '.' you can enter a file or directory to go to. <Tab> and <Backspace> (or <Delete>) will slide the labels (aka the "bag") around to the other files on the screen. <Space> will page to the next screenful of files in the current directory. Typing 'L' repeatedly will display the long listings of the files in the bag's column (<Control-L> will clear the long listings). ':' will let you run a shell command. 'V' will suspend vshnu, dropping you back into the invoking shell. <Control-Q>q (or <Control-Z>q) will exit vshnu.

With the mouse, you can left-click on a subdirectory name to enter it, or on a filename to load it into your editor. Center-click on the background to go up to the parent directory, or right-click there to go back to the previous directory. Use the mouse scroll wheel on the background to page to other screenfuls of files in the current directory, or on the time to display the long listings (right-clicking on the time will clear the long listings).

Of course, there's much, much more possible. Type '%' within each mode of vshnu to see all the key commands available and what they'll do. Type '&' to see what file actions will be performed upon selecting files in the current file action mode. Type <Control-N> followed by a key to see what would happen with that key command. Type '^' to see all the available mouse commands.

Here's a summary of the modes in the supplied configuration, with the keys to enter and exit each mode:

MODE	KEY	KEY COMMAND MODES
main		The starting mode and most commonly used.
choose	/	Selected files are added to the set of chosen files. Main mode commands are available here, too, though a few change meaning. Additional key commands are available that operate on the chosen file set.
opts	O	Sets and unsets various options for sorting and listing the display. Type '%' in opts mode for a complete options list. This mode exits automatically after an option key is selected.

MODE	KEY	FILE ACTION MODES
edit		The starting mode where files are editted and directories are entered.
do	?	Special action is taken depending on the nature of the file selected, eg, GIF files are viewed, archive files have their contents listed, etc.
expand	"	Selected directories are expanded in the file listing, or collapsed if they're already expanded.

• The latest developer's version of the vshnu source files are available: vshnu, vshnucfg.pl, vshnurc.pl

• A web forum and mailing list for discussion, support and announcements regarding vshnu was available at <https://web.archive.org/web/20201023100844/https://groups.yahoo.com/neo/groups/vshnu/info>

• An introductory article on using vshnu was published in the November 2005 issue of Linux Magazine (US version) in Jerry Peek's Power Tools column, pages 12-17. It's available online at <http://www.jpeek.com/articles/linuxmag/2005-11/>. There's also a bit in Hebrew online at <https://web.archive.org/web/20170312061951/http://linmagazine.co.il/book/view/8177>.

• CaFe.pm <http://cafe.pm.org/>, a Perl Mongers group in Argentina, has published an interview by Víctor A Rodríguez with Steve Kinzler about vshnu in their April 2006 bulletin, issue 1.0. It's available online at <http://cafe.pm.org/boletines/Issue.v1.0.pdf>, with the original English version at <https://kinzler.com/me/vshnu/perlitas.html>.

• A Japanese review and showcase of vshnu was published in the September 2001 issue of Linux Magazine, pages 124-125.

• A Romanian translation of this page by Maxim Petrenko.

vshnu: the New Visual Shell
Copyright © 1999 Stephen B Kinzler

Unix Home Dir	https://kinzler.com/me/home.html Many scripts and config files for Unix/X11 environments
align	https://kinzler.com/me/align A text column alignment filter
vshnu	https://kinzler.com/me/vshnu A visual shell and CLI shell supplement
webrowse	https://kinzler.com/me/webrowse Tools to interface web browsers to the Unix user CLI
xtitle	https://kinzler.com/me/xtitle Set window title and icon name for an X11 terminal window
z	https://kinzler.com/me/z A convenience frontend for tar, gzip, zip, etc

Steve Kinzler <steve@kinzler.com> https://kinzler.com/me
November 2000, revised January 2022