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rcat.icn
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2000-07-29
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############################################################################
#
# File: rcat.icn
#
# Subject: Program to output a file from back to front
#
# Author: Gregg M. Townsend
#
# Date: March 7, 2000
#
############################################################################
#
# This file is in the public domain.
#
############################################################################
#
# This program outputs in reverse order the lines of one or more files.
# Unlike some versions of "tail -r", the input file does not need to
# fit in memory; but it must be seekable.
#
# usage: rcat file...
#
############################################################################
$define BUFSIZE 65536
procedure main(args)
local f, fname, len, i, nseg, buf, leftover, lines
if *args = 0 then
stop("usage: ", &progname, " file...")
every fname := !args do {
lines := []
leftover := ""
f := open(fname, "u") | stop("cannot open ", fname)
len := where(seek(f, 0)) - 1 | stop("cannot seek ", fname)
nseg := (len + BUFSIZE - 1) / BUFSIZE
every i := nseg - 1 to 0 by -1 do {
seek(f, 1 + BUFSIZE * i)
(reads(f, BUFSIZE) || leftover) ? {
leftover := tab(upto('\n') + 1 | 0)
while push(lines, tab(upto('\n') + 1))
if not pos(0) then
push(lines, tab(0))
}
while writes(get(lines))
}
writes(leftover)
}
end