File: esh-var.el.html

These are the possible variable interpolation syntaxes. Also keep in mind that if an argument looks like a number, it will be converted to a number. This is not significant when invoking external commands, but it's important when calling Lisp functions.

  $VARIABLE

Interval the value of an environment variable, or a Lisp variable

  $ALSO-VAR

"-" is a valid part of a variable name.

  $\"MYVAR\\"-TOO
  $'MYVAR'-TOO

Only "MYVAR" is part of the variable name in this case.

  $(lisp)

Returns result of Lisp evaluation. Note: Used alone like this, it is identical to just saying (lisp); but with the variable expansion form, the result may be interpolated a larger string, such as
'$(lisp)/other'.

  ${command}

Returns the value of an eshell subcommand. See the note above regarding Lisp evaluations.

  $<command>

Evaluates an eshell subcommand, redirecting the output to a temporary file, and returning the file name.

  $EXPR[10]

Return the 10th element of $EXPR, which can be any dollar expression. If $EXPR's value is a string, it will be split in order to make it a list. The splitting will occur at whitespace.

  $EXPR[10 20]

As above, but instead of returning a single element, it now returns a list of two elements.

  $EXPR[: 10]

Like $EXPR[10], except that splitting occurs at the colon now.

  $EXPR["\\\\\\\\" 10]

Separate on backslash characters. Actually, the first argument -- if it doesn't have the form of a number -- can be any regular expression. So to split on numbers, use '$EXPR["[0-9]+" 10 20]'.

  $EXPR[hello]

Calls assoc on $EXPR with 'hello', expecting it to be an alist.

  $#EXPR

Returns the length of the value of $EXPR. This could also be done using the length Lisp function.

There are also a few special variables defined by Eshell. '$$' is the value of the last command (t or nil, in the case of an external command). This makes it possible to chain results:

  /tmp $ echo /var/spool/mail/johnw
  /var/spool/mail/johnw
  /tmp $ dirname $$
  /var/spool/mail/
  /tmp $ cd $$
  /var/spool/mail $

'$_' refers to the last argument of the last command. And $?
contains the exit code of the last command (0 or 1 for Lisp functions, based on successful completion).

Defined variables (9)

Defined functions (28)

Defined faces (0)