Special characters in alias

Question

Is it possible to have special characters in alias?

A very dumb example, just to make the point:

ls | xargs cat | grep "this"
alias ->='xargs cat | grep '
ls | -> "this"

Answer 1

According to the bash man page, an alias must be a "name":

alias [-p] [name[=value] …]

... If arguments are supplied, an alias is defined for each name whose value is given.

and:

name

A word consisting solely of letters, numbers, and underscores, and beginning with a letter or underscore. Names are used as shell variable and function names. Also referred to as an identifier.

Answer 2

As of 5.2.15, at least, the man page states:

The characters /, $, `, and = and any of the shell metacharacters or quoting characters listed above may not appear in an alias name.
...
metacharacter
       A character that, when unquoted, separates words. One of the following:
       | & ; ( ) < > space tab newline
...
There are three quoting mechanisms: the escape character, single quotes, and double quotes
       A non-quoted backslash (\) is the escape character.

In fact I didn't get to work the opening square bracket (it does work in dash), "[", the alias definition doesn't complain, but unable to "call" it later, I get:

unexpected EOF while looking for matching ``'

And escaping it with back slash doesn't match:

pm_7_aa[: command not found

However, if the first character of the alias name is itself a square bracket, it works...

It can be useful in this kind of syntax:

pm_7_aa{_ "$var" ; _}
[pm_7_aa: "$var" ; :]
pm_7_aa_[ "$var" ; ]_ # Only in dash as said

As a quirk for sending arguments to aliases, by using an open alias (to process the arguments calling a function) and a close alias (for example to set the positional parameters or define a local variable). Some kind of macros with aliases, I find it a very powerful syntax sugar.

For this question, it could then be:

 alias -- -}='xargs cat | grep ' # For bash
 alias -}='xargs cat | grep ' # For dash
 ls | -} "this"

Answer 3

Yes it's perfectly possible to use special characters inside an alias or a function name.

Ex. :

alias ls∂="ls -al | grep '^d'"
ls∂() { ls -al | grep '^d' ; }

On the other hand it's clearly risky explosive business to use meta characters inside an alias or a function name.