tcsh csh on Steroids

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tcshcsh on Steroids
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tcsh

• Derived from csh, Bill Joy's creation from
  Berkeley
• Based on Joy's original source, many, many people
  have added to it since
• Over 50 names are listed as contributors in the
  6.08 man page
• Freely available over the internet
• Compatible with csh
• All the commands and capabilities you are used to
  in csh are available in tcsh
• If it works in csh, it should also work in tcsh

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The 't' in tcsh

• In 1964, DEC produced the PDP-6.
• The PDP-10 was a later re-implementation that
  was re-christened the DECsystem-10 in 1970 or
  so when DEC brought out the second model, the
  KL10.
• TENEX was created at Bolt, Beranek Newman
• A Cambridge, Mass. think tank also referred to
  as BBN, one of the early implementers of the
  Internet
• Done in 1972 as an experiment in demand-paged
  virtual memory operating systems.
• They built a new pager for the DEC PDP-10
  and created the OS to go with it.
• It was extremely successful in academia.

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• In 1975, DEC brought out a new model of the
  PDP-10, the KL10
• Intent was to have only a version of TENEX, which
  they had licensed from BBN, for the new box,
  which they called TOPS-20 (the capitalization
  is trade-marked).
• A lot of TOPS-10 users (The OPerating System
  for PDP-10') objected thus DEC found themselves
  supporting two incompatible systems on the
  same hardware--but then there were 6 on the
  PDP-11!

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• TENEX, and TOPS-20 up until version 3, had
  command completion via a user-code-level
  subroutine library called ULTCMD.
• With version 3, DEC moved all that capability and
  more into the monitor ('kernel' in Unix lingo)
• The creator of tcsh was impressed by this feature
  and several others of TENEX and TOPS-20, and
  created a version of csh which mimicked them.

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Advantages of tcsh over csh

• Command-line editing
• Better word completion
• tcsh can complete command and variable names in
  addition to filenames
• Spelling correction
• Assistance for entering hard to type filenames
• Built-in rm detection

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Startup and Configuration Files

• /.cshrc - Read at startup
• /.tcshrc - Read at startup instead of ./cshrc
• if it exists
• /.login - Read by login shells at startup
• /.history - Saves command history list
• /.cshdirs - Saves the directory stack
• /.logout - Read by login shells at termination

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Command-line Editing

• Like the Korn shell, tcsh provides an emacs and
  vi command-line editing mode
• Selected by "bindkey -e" or "bindkey -v" command
• Generally placed in your /.tcshrc file
• One advantage over Korn shell editing is that you
  are always in the command-line editor!
• Normal mode is insert, which is how you enter
  commands
• Various editing commands are available in insert
  mode

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Insert Mode Editing Commands

• CTRL-B Move cursor back one char
• CTRL-F Move cursor forward one char
• CTRL-A Move to beginning of line
• CTRL-E Move to end of line
• CTRL-H or DEL Delete char to left of cursor
• CTRL-W Delete word backward
• CTRL-U Delete from beginning of line
• to cursor
• CTRL-K Delete from cursor to end of
• line

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Command Mode

• Use ESC to enter command mode
• Normal vi commands are then in effect
• Don't forget to issue the "bindkey -v" command
  first or things will act very confusingly!
• You can also use the command editor to retrieve
  and execute commands from the history list
• CTRL-P (previous) and CTRL-N (next) are used to
  move up and down through the history list
• ? and / can also be used to search backwards and
  forwards through the history list

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Repeating Commands in a Loop

• If you want to run a command once for each of a
  set of filenames, you can use a foreach loop
• foreach fn (file1 file2 file3 file4)
• ? cat fn spell fn.spl
• ? end
• After you enter the foreach line, the shell
  changes the prompt as it collects the body of the
  loop and then executes it after the end is
  entered

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Word Completion

• In csh if filec is set, it will attempt to
  complete filenames for you when you hit the TAB
  key
• If the prefix you type is ambiguous, CTRL-D will
  list all potential matches
• In tcsh, command completion is always active
• To exclude certain filename suffixes from being
  considered, set fignore ( .o .bak ) in your
  /.tcshrc file

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Patterns

• You can use patterns (, ?, ) to define
  filenames
• tcsh also adds and pattern
• You can also use patterns for filenames that
  don't exist
• The are used for specifying non-existent
  files
• For example
• mkdir tempdir1-4
• mkdir No match
• However
• mkdir tempdir1,2,3,4

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Assistance in Entering Difficult Filenames

• Filename completion is usually the easiest way to
  deal with difficult to type filenames
• tcsh uses a backslash (\) to escape special
  characters
• For example, with a file named "My Favorite Lab
  Pt II"
• mv My Hit TAB
• mv My\ Favorite\ Lab\ Pt\ II tcsh provides rest
  of name
• mv My\ Favorite\ Lab\ Pt\ my_fav_lab_2
• Type rest of command
• csh does not have this capability

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-'s as Leading Chars in Filenames

• Though not tcsh specific, how do you delete a
  file that has a leading - in it's filename?
• Most commands see a - as signifying an option
• rm -filename
• usage rm -rif file
• Hmmm

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• Easiest way is usually to preface the filename
  with its path
• rm ./-filename
• The character can cause the same kind of
  problems

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Spelling Correction

• To enable spelling correction, add one of the
  following to /.tcshrc
• set correct cmd
• set correct all
• The first option causes spelling correction to be
  applied for commands only
• The second tries to correct all entries on the
  command line
• You need to be careful with correct all

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• When the shell thinks you have misspelled a word,
  it suggests a correction
• mroe lab3
• CORRECTmore lab3 (ynea)?
• yesnoeditabort
• Now, suppose I enter the following command
• mv lab3 lab4
• CORRECTmv lab3 lab3 (ynea)?
• What is the problem?

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Automatic rm Detection

• If the shell variable rmstar is set, tcsh will
  detect attempts to use rm
• rm
• Do you really want to delete all files? n/y
• If you want to overide it, use the force option
  with rm
• rm -f

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Directory Stacks

• Moving between two directories in tcsh is simple
• "cd -" returns you to your previous directory
• For more control with multiple directories, both
  csh and tcsh allow a directory stack
• pushd and popd, along with dirs are used with the
  stack
• pushd dirname changes to that directory and
  pushes the directory onto the stack
• popd changes to the directory on the top of the
  stack
• dirs lists the contents of the stack without
  changing your current directory

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• pushd without a directory name exchanges the top
  two elements of the stack
• You can also use pushd n to rotate the stack so
  that entry n is on top
• If stack has dir1 dir2 and dir3, pushd 2 would
  give
• dir3 dir1 dir2
• popd n pops entry n from the stack, changing to
  it (tcsh only though some versions of csh may do
  it)

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Stack Example

• Say I start in /home/bonnie/cc9
• pushd krf current dir is /home/bonnie/krf
• stack krf cc9
• pushd src current dir is /home/bonnie/krf/src
• stack krf/src krf cc9
• pushd java current dir is /home/bonnie/krf/src/jav
  a
• stack krf/src/java krf/src krf cc9
• pushd current dir is /home/bonnie/krf/src
• stack krf/src krf/src/java krf cc9
• popd current dir is /home/bonnie/krf/src/java
• stack krf/src/java krf cc9
• pushd ../C current dir is /home/bonnie/krf/src/C
• stack krf/src/C krf/src/java krf cc9

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• popd current dir is /home/bonnie/krf/src/java
• stack krf/src/java krf cc9
• popd current dir is /home/bonnie/krf/
• stack krf cc9
• popd current dir is /home/bonnie/cc9
• stack cc9

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tcsh Specific Shell Variables

• correct - Enable spelling correction
• rmstar - Enable "rm " detection
• savedirs - Save the directory stack in
• /.cshdirs on logout
• tcsh - Holds tcsh version number
• version - Holds shell version and
• configuration information

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tcsh Prompts

• csh didn't have a whole lot of special things you
  could put in your prompt
• \! to add the command number followed by - was
  it!
• tcsh adds a number of other useful options
• t, p (T, P), D, W, and y
• time, time plus seconds (24 hour versions), day,
  month, and year Example set prompt "The time
  is t "
• B/b bolds/unbolds
• U/u underlines/ends underline
• S/s starts/ends standout
• Other options are listed in the man page
• Check 'em out!