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############################################################################
#
# File: fset.icn
#
# Subject: Program to do set operations on file specifications
#
# Author: Thomas R. Hicks
#
# Date: June 10, 1988
#
############################################################################
#
# This file is in the public domain.
#
############################################################################
#
# The UNIX shell provides for the specification of filenames
# using ``wildcards''. Each wildcard specification may be
# thought of as defining a set of names (that is, those that
# match the specification). Fset allows the user to apply the
# set operations of intersection, union, and difference to
# these filename sets. The resultant list may then be used as
# an argument to other shell commands.
#
# Fset's argument is an expression composed of legal UNIX file
# specifications, parenthesis, and the following set opera-
# tors:
#
# && intersection
# ++ union
# -- difference
#
# Because characters that have special meaning to the shell
# occur frequently in the arguments used for fset, it is
# advisable to quote the arguments consistently.
#
# The use of fset is illustrated by the following examples:
#
# fset 'g*--*.icn'
#
# produces the list (set) of filenames for files beginning
# with g, excluding those ending with .icn.
#
# Similarly,
#
# fset '*'
#
# produces all files in the current directory excluding the .
# and .. files.
#
# fset '((*--*.icn)++c*)'
# and
#
# fset '(*--*.icn)++c*'
#
# produces the complement of all filenames ending with .icn in
# addition to all filenames beginning with c.
#
# fset '(((c? && c*)))'
#
# is a redundant, but legal, specification for all two-
# character filenames that begin with c, while
#
# fset '.*'
#
# produces the set of filenames for all hidden files, exclud-
# ing the . and .. files.
#
# Limitations:
#
# Multiple command line arguments, formed by omitting the
# quotes around the file set expression, are permitted. Their
# use is limited, however, since parentheses do not get past
# the shell's command-line expansion.
#
# Almost any legal file specification will work when enclosed
# in quotes except that the simple grammar that is used cannot
# handle blanks adjacent to parentheses.
#
# File names that begin or end in ``questionable'' characters
# such as *, ?, +, -, and &, probably will not work.
#
# A file specification that, when interpreted by the shell,
# produces no matching filename will be placed (unchanged) in
# the result.
#
############################################################################
#
# See also: gcomp.icn
#
############################################################################
#
# Requires: UNIX
#
############################################################################
procedure main(args)
local i, fyls, arglist
if *args = 0 then return
if *args > 1 then
every i := 2 to *args do
args[1] ||:= (" " || args[i])
(arglist := parse(args[1])) |
stop("Invalid file specification expression")
case type(arglist) of {
"string" : fyls := mkfset(arglist)
"list" : fyls := exec(arglist)
default : stop("Main: bad type -can't happen")
}
fyls := sort(fyls)
every write(!fyls," ")
end
procedure Exp() # file spec expression parser
local a
suspend (a := [Factor(),=Op(),Factor()] & [a[2],a[1],a[3]]) |
Factor() |
(a := [="(",Exp(),=")"] & .a[2])
end
procedure Factor() # file spec expression parser
local a
suspend (a := [Term(),=Op(),Term()] & [a[2],a[1],a[3]]) |
Term() |
(a := [="(",Factor(),=")"] & .a[2])
end
procedure Name() # file spec name matcher
static valid
initial valid := ~'()'
suspend (any(~valid) || fail) | tab(find(Op()) | many(valid))
end
procedure Non() # file spec expression parser
local a
suspend a := [Name(),=Op(),Name()] & [a[2],a[1],a[3]]
end
procedure Op() # file spec operation matcher
suspend !["++","--","&&"]
end
procedure Term() # file spec expression parser
local a
suspend (a := [="(",Non(),=")"] & .a[2]) |
Name()
end
procedure bldfset(arg) # build file set, excluding . and ..
local line
static dotfiles
initial dotfiles := set([".",".."])
line := read(open("echo " || arg,"rp"))
return str2set(line,' ') -- dotfiles
end
procedure exec(lst) # process file spec list recursively
return setops(lst[1])(exec2(lst[2]),exec2(lst[3]))
end
procedure exec2(arg) # helping procedure for exec
case type(arg) of {
"string" : return mkfset(arg)
"list" : return exec(arg)
default : stop("exec2: can't happen")
}
end
procedure mkfset(fspec) # make file list from specification
if fspec == "*" then
fspec := "* .*"
return bldfset(fspec)
end
procedure parse(str) # top level of parsing procedures
local res
str ? (res := Exp() & pos(0)) | fail
return res
end
procedure sdiff(f1,f2) # set difference
return f1 -- f2
end
procedure setops(op) # return correct set operaton
case op of {
"++" : return sunion
"&&" : return sinter
"--" : return sdiff
}
end
procedure sinter(f1,f2) # set intersection
return f1 ** f2
end
procedure str2set(str,delim) # convert delimited string into a set
local fset, f
fset := set()
str ? {
while f := (tab(upto(delim))) do {
insert(fset,f)
move(1)
}
if "" ~== (f := tab(0)) then
insert(fset,f)
}
return fset
end
procedure sunion(f1,f2) # set union
return f1 ++ f2
end
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