Writing "Hello World" in Emacs?

I would like to write a few Unix scripts in Emacs Lisp. However, there doesn't seem to be a clean way to write to STDOUT so I can redirect the results to a file or pipe the output to another command. The print function places double quotes around the output strings so I get "Hello world!" instead of Hello world!.

Here's the emacs script.

#!/usr/bin/emac开发者_JAVA百科s --script
;;
;; Run me from a Unix shell: ./hello.el > x.txt
;;
(message "Hello world!  I'm writing to STDERR.")
(print "Hello world!  I'm writing to STDOUT but I'm in quotes")
(insert "Hello world!  I'm writing to an Emacs buffer")
(write-file "y.txt")

And here's how I would like to call it.

hello.el > x.txt
hello.el | wc

Seems like you want princ instead of print. So, basically:

(princ "Hello world! I'm writing to STDOUT but I'm not in quotes!")

However, one caveat is that princ does not automatically terminate the output with \n.

As David Antaramian says, you probably want princ.

Also, message supports a format control string (akin to printf in C) that is adapted from format. So, you may eventually want to do something like

(princ (format "Hello, %s!\n" "World"))

As a couple of functions plus demonstration:

(defun fmt-stdout (&rest args)
  (princ (apply 'format args)))
(defun fmtln-stdout (&rest args)
  (princ (apply 'format
                (if (and args (stringp (car args)))
                    (cons (concat (car args) "\n") (cdr args))
                  args))))

(defun test-fmt ()
  (message "Hello, %s!" "message to stderr")
  (fmt-stdout "Hello, %s!\n" "fmt-stdout, explict newline")
  (fmtln-stdout "Hello, %s!" "fmtln-stdout, implicit newline"))