File: esh-worker.el.html

Workers are an Emacs Lisp-based analogue to external processes, allowing for piping command output into them to perform some action. For example, to uppercase the output of some other command:

  echo hi | #'upcase

;_* accumulate worker

Eshell provides several ways to pipe output into a Lisp function. The simplest is the "accumulate" worker, which is the default behavior when piping directly to a Lisp function as above. You can also express this explicitly, as in:

  echo hi | accumulate #'upcase

;_* map-lines worker

You can also map each line of output to a function, similar to how mapcar works. For example, you could "quote" some output for pasting into an email like this:

  cat some-file.txt | map-lines (lambda (i) (format "> %s" i))

This also shows how you use lambda functions as pipe targets in Eshell.

;_* apply-lines worker

Finally, you can apply each line of output as successive arguments to a function. For example, to sum up a list of numbers written one per line:

  cat numbers.txt | apply-lines #'+

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