sed is an actively used programming language created in 1974.

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Example code from Linguist:

# Towers of Hanoi in sed.
#	@(#)hanoi.sed	8.1 (Berkeley) 6/6/93
# $FreeBSD$
# Ex:
# Run "sed -f hanoi.sed", and enter:
#	:abcd: : :<CR>
# note -- TWO carriage returns were once required, this will output the
# sequence of states involved in moving 4 rings, the largest called "a" and
# the smallest called "d", from the first to the second of three towers, so
# that the rings on any tower at any time are in descending order of size.
# You can start with a different arrangement and a different number of rings,
# say :ce:b:ax: and it will give the shortest procedure for moving them all
# to the middle tower.  The rules are: the names of the rings must all be
# lower-case letters, they must be input within 3 fields (representing the
# towers) and delimited by 4 colons, such that the letters within each field
# are in alphabetical order (i.e. rings are in descending order of size).
# For the benefit of anyone who wants to figure out the script, an "internal"
# line of the form
#		b:0abx:1a2b3 :2   :3x2
# has the following meaning: the material after the three markers :1, :2,
# and :3 represents the three towers; in this case the current set-up is
# ":ab :   :x  :".  The numbers after a, b and x in these fields indicate
# that the next time it gets a chance, it will move a to tower 2, move b
# to tower 3, and move x to tower 2.  The string after :0 just keeps track
# of the alphabetical order of the names of the rings.  The b at the
# beginning means that it is now dealing with ring b (either about to move
# it, or re-evaluating where it should next be moved to).
# Although this version is "limited" to 26 rings because of the size of the
# alphabet, one could write a script using the same idea in which the rings
# were represented by arbitrary [strings][within][brackets], and in place of
# the built-in line of the script giving the order of the letters of the
# alphabet, it would accept from the user a line giving the ordering to be
# assumed, e.g. [ucbvax][decvax][hplabs][foo][bar].
#			George Bergman
#			Math, UC Berkeley 94720 USA

# cleaning, diagnostics
s/  *//g
Illegal characters: use only a-z and ":".  Try again.
Incorrect format: use\
\	: string1 : string2 : string3 :<CR>\
Try again.
Repeated letters not allowed.  Try again.
# initial formatting
s/[a-z]/ /g
s/^:\( *\):\( *\):\( *\):\n:\([a-z]*\):\([a-z]*\):\([a-z]*\):$/:1\4\2\3:2\5\1\3:3\6\1\2:0/
# outputting current state without markers
# establishing destinations
# iterate back to find smallest out-of-place ring
# move said ring (right, resp. left)
s/^\(.\)\(.*\)\1\([23]\)\(.*:\3[^ ]*\) /\1\2 \4\1\3/
s/^\(.\)\(.*:\([12]\)[^ ]*\) \(.*\)\1\3/\1\2\1\3\4 /
s/.*/Done!  Try another, or end with ^D./p

Example code from Wikipedia:

This is my dog, whose name is Frank.
This is my fish,
whose name is George.
This is my goat, whose name is Adam.

Last updated February 11th, 2019