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How do I assign alias(es) to my Tc Shell (tcsh)?
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Syntax for Defining Alias
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Alias is a pseudonym or shorthand for a command or series of commands, i.e.,
a convenient macro for frequently used command or a series of commands.
An alias definition affects the current shell execution
environment and the execution environments of the subshells
of the current shell. The alias definition will
not affect the parent process of the current shell
nor any utility environment invoked by the shell.
For Tc shell (tcsh), you can define alias(es) using
-
alias alias_name 'command'
syntax in .tcshrc file in your root directory. You can define as many aliases as you want
(as long as you can remember alias names) in .tcshrc. Keep in mind that if you do not have a
.tcshrc file in your home directory, then Tc shell will automatically
sourcing out .cshrc.
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For example, to create a simple command alias, first open your
.tcshrc file in your home directory using any text editor of
your choice. (if you do not have a .tcshrc file in your
home directory, then open .cshrc and add aliases)
-
alias del 'rm -i'
This creates an alias del for the command
"rm -i" which prompts you for confirmation that you want to remove a
file before it does so.
To create a command alias that consists of a series of commands,
-
alias ll '/usr/bin/ls -Flsa |more'
This creates an alias ll for the command
"ls" with "Flsa" flags and pipe the result to "more" command to
display the result one screenful at a time.
Of course, you can refer to another command alias within an alias,
-
alias h history
alias rev 'h | tail -10'
The first command assigns an alias h to the
"history" command. The next
command assigns another alias rev to the
command "h | tail -10". This takes the output from the alias h (= the "history" command) and pipes it through
the "tail" command to list the
ten most recent commands in the command history.
Here an example to pass command arguments to the alias,
-
alias print 'lpr \\!^ -Php4'
Now, to print a file to the CEE UCL default printer "hp4,"
you can enters a command such as:
-
$ print ohboy.f
The notation "!^" causes the first argument to the command
alias print to be inserted in
the command at this point. The command that is carried out is:
-
lpr ohboy.f -Php4
Of course, you can also pass multiple arguments to a command alias.
-
alias mprint 'lpr \\!* -Php4'
The notation "!*" causes multiple arguments given to the alias
mprint to be inserted in
the command. If you enters following command
-
$ mprint ohboy.f headache.txt huge_bug_list.ps
the actual command would look like
-
lpr ohboy.f headache.txt huge_bug_list.ps -Php4
Notice that the "!" character is preceeded by a
"\\" to prevent it being interpreted by Tc shell as a metacharacter.
The reason is that "!" is one of shell metacharacters
that are inetrpreted as something other than the character or symbol
by the shell. FYI, here's a list of all metacharacters for Tc shell.
- ; & ( ) | ^ < > ~ % { }
- $ # ' " \ @@ * ? [ ] - !
- Newline (a <Return>)
- Space (a <Space>)
- Tab (a <Tab>)
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- To display the value of an alias known to the shell,
type;
-
$ alias
To display the current value for a particular alias, use
the command;
-
$ alias name_of_alias
For example, to display the current value of the alias
named print;
-
$ alias print
lpr \\!^ -Php4
- Once alias definition is save in .tcshrc, the alias will be in effect next time you
login. If you wish to make the alias in effect immediately, update your
alias definition by sourcing out .tcshrc.
Keep in mind that if you do not have a .tcshrc file in your home directory, then Tc shell
will automatically sourcing out .cshrc.
-
$ source .tcshrc
- To cancel a command alias during your current login
session use the command;
-
$ unalias name_of_alias
For example,
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$ unalias print
will cancel the command alias print for your
current login session. You will have to remove the alias definition from
your .tcshrc file if you want to cancel the
alias permanently.
For further details, RTFM on "alias."
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