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############################################################################
#
# File: getlines.icn
#
# Subject: Program to extract lines from a file
#
# Author: Ralph E. Griswold
#
# Date: March 26, 2002
#
############################################################################
#
# This file is in the public domain.
#
############################################################################
#
# This program is designed to extract a few specified lines from a file.
# The line numbers are given on the command line, the file is read from
# standard input and the extracted lines are written to standard output
# as in
#
# getlines 46 23 119 <infile >outfile
#
# which writes lines 23, 46, and 119 of infile (if it contains that many
# lines) to outfile.
#
# Line numbers do not have to be given in order. Numbers less than 1 are
# ignored, but a nonnumerical argument is treated as an error.
#
############################################################################
procedure main(lines)
local i, line
if *lines = 0 then stop("*** no lines specified")
every i := 1 to *lines do
lines[i] := integer(lines[i]) |
stop("*** nonnumeric argument: ", image(lines[i]))
lines := set(lines) # inefficient method but easy
i := 0
while line := read() do {
i +:= 1
if member(lines, i) then {
write(line)
delete(lines, i) # so process can be stopped before end
if *lines = 0 then exit()
}
}
end
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