Features of C shell

Each shell has its own set of features. Those of the C Shell are discussed below.

• Command history: The history mechanism maintains a list of recently used command lines, called events. Provides a shorthand for reexecuting previous commands. To use history:
1. Set the history variable:

     set history = 100

2. Issue the history command and view the output:

     history



     35  12:34   sort < unsorted > sorted.list

     36  12:34   cat sorted.list

     37  12:35   ls * > unsorted

     38  12:35   cat unsorted

     39  12:35   ls

     40  13:06   history

     41  13:08   alias

     42  13:11   ls

     43  13:11   vi .cshrc

3. To save history events across all login sessions, set the savehistory variable:

     set savehistory = 50

• Event reexecution: Allows you to specify a shorthand for reexecuting a previous event. Works with the history list.

     !!          - repeats last command 

     !number     - repeats numbered command from history list

     !string     - repeats last command starting with string 

• Modifying previous events: Allows you to correct typos in previous command, or modify it to create a new command.

     ^old^new             - changes the string "old" to the 

                            string "new" in the last command  

                            issued 

     !number:s/old/new/   - changes numbered command from 

                            history list; substitutes the 

                            string "old" with the string "new".

                            Note that there is no space 

                            between number and : 

         

• Aliases: The alias command allows you to define new commands. Useful for creating shorthands for longer commands. The syntax is.

     alias  entered_command  executed_command

Some examples:

     alias  m     more

     alias  rm    "rm -i"

     alias  h     "history -r | more"

     alias  xpvm  /source/pd/xpvm/src/RS6K/xpvm

To view all current aliases:

     alias

To remove a previously defined alias:

     unalias alias_name

• Filename Generation: When you give the shell abbreviated filenames which contain special characters (metacharacters), it can generate filenames which match existing files. Some examples appear below:

     

     ls  *.txt    - list files with .txt suffix 

     ls [abc]*    - list files with names that start with a, 

                    b or c

     lpr prog?.c  - print files named prog?.c where ? is 

                    any character

     cd ~jsmith   - change to user jsmith's home directory

You can "turn off" filename generation by setting the noglob variable. This will permit special characters to be interpreted literally. For example:

     set noglob

• Filename Completion: The shell will complete a filename for you if you type in only enough characters to make the name unique. This feature is a great time saver and helps to prevent typos when trying to type long filenames.
To use filename completion, you need to set filec, either on the command line or in one of your initialization files.


     set filec

Then, when specifying a filename, type the part which is unique and hit the escape key (C shell) or tab key (TC Shell). For example, if you had a directory with a long name, such as "Introduction.UNIX.Filesystems", you could cd to that directory by using the cd command with only a portion of the file's name, provided that the portion you specify is unique (no other files have similar names)

     

     cd Intro

Note: typing a portion of a filename and then hitting CTRL-D instead of ESCape or TAB will display a list of the filenames which match.