NAME¶
Slice -- Extract pre-defined slices from an ASCII file
SYNOPSIS¶
slice [
-v] [
-y outputpolicy] [
-o
sliceterm:
outputfile[@
chmodcmd][#
outputpolicy]
..] [
inputfile]
slice [
-V] [
-h]
VERSION¶
1.3.8 (10-Feb-2002)
DESCRIPTION¶
The
slice program reads
inputfile (or from
STDIN if
inputfile is not given or equal ``"-"'') and divides its
already prepared ASCII contents into possibly overlapping areas, called
slices. These slices are determined by enclosing blocks defined by
begin and end delimiters which have to be
already in the file. These
block delimiters use the syntax
[NAME: ... :NAME]
or alternatively (if there is no misinterpretation possible, i.e. no overlapping
or stacked slices)
[NAME: ... :]
The
NAME identifier has to match against the regular expression
``"[_A-Z0-9]+"'', i.e.
NAME is a string consisting only of
uppercase letters, digits or underscore characters.
There can be as many such slice definitions as you like and there can be more
than one slice with the same name. The resulting slice is the union of all
equal named slices. Actually use this to spread a big slice over disjunct
peaces of
inputfile.
Output Selection Scheme¶
The final output data gets calculated by a slice term consisting of slice names
and set theory operators. The following syntax is recognized (in order of
LR(1) grammar parsing) for slice terms:
- SLICE_TERM ::= "NAME"
- The slice NAME itself. This name has to match against the
regex ``"[_A-Z0-9*{}]+"''. Here two cases are possible:
"NAME" is either a plain slice name consisting only of uppercase
letters, digits or an underscore character. Or it is a wildcarded slice
name indicated by an asterisk character.
The first variant just expands to the union of all slices named exactly
"NAME". The second variant expands to the union of all slices
which match against the wildcard pattern "NAME". Here the
asterisk has the semantical meaning of none or any number of characters.
There is one special case, when the asterisk is immediately followed by
characters enclosed within braces, it means none or any number of
characters, but not this sequence of characters.
- SLICE_TERM ::= "!NAME" | "~NAME"
- The complement of slice NAME (i.e. ALL\NAME).
In formula: {x in ALL: x not in NAME}
- SLICE_TERM ::= "NAME1xNAME2",
"NAME1^NAME2"
- The exclusive-or relation between slice NAME1 and
slice NAME2. In set theory also called symmetric difference:
(NAME1uNAME2)\(NAME1nNAME2) or alternatively
(NAME1n!NAME2)u(!NAME1nNAME2).
In formula: {x in ALL: (x in NAME1 or x in NAME2) and not (x in NAME1 and x
in NAME2)}.
- SLICE_TERM ::= "NAME1\NAME2",
"NAME1-NAME2"
- The difference of slice NAME1 and slice NAME2, i.e.
NAME1 minus NAME2.
In formula: {x in ALL: x in NAME1 and x not in NAME2}
- SLICE_TERM ::= "NAME1nNAME2" |
"NAME1%NAME2"
- The intersection of slice NAME1 and slice NAME2.
In formula: {x in ALL: x in NAME1 and x in NAME2}
- SLICE_TERM ::= "NAME1uNAME2",
"NAME1+NAME2"
- The union of slice NAME1 and slice NAME2.
In formula: {x in ALL: x in NAME1 or x in NAME2}
- SLICE_TERM ::= "(" SLICE_TERM ")"
- A grouped slice term. Use this to force a different order
of evaluation. By default, all operators are left-associative, except
complement which is right-associative. Operators are listed below from
lowest to highest precedence:
- u x n !
Advanced Selection: Slice Levels¶
Because slices can be overlapping and stacked, a definition level is assigned to
each slice while the input is parsed. These levels range from 1 to the maximum
encountered (the level 0 is the whole file, i.e. "ALL"). When a
slice begins, it is assigned the lowest free level, beginning with level 1. As
long as one level is in use, it cannot be assigned again until the end
delimiter of the corresponding slice is seen.
An example:
[A:[B::B]:A][C:[D:[E::C]:D][F::E]:F]
3 E-----------E
2 B--B D--------D
1 A--------A C--------C F-----F
0
Here slice A is assigned level 1. Then B is assigned level 2 because level 1 is
still in use by A. Then the end of B is reached, level 2 is freed. Then the
end of A is reached and level 1 is also free now, so C is assigned level 1
again. Now only level 1 is in use, so D is assigned level 2. Then E is
assigned level 3. Then the end of C is seen and level 1 freed. Then the end of
D is seen and level 2 is freed. Now F begins and because only level 3 is in
use, it gets level 1 assigned. Then the end of E frees level 3 and the end of
F frees level 1. Finally no levels are still in use. This indicates that the
slicing is correct.
If there are any used levels left at the end of this process this indicates an
input error and
slice responds with an error message displaying the
still open slices.
This complicated level mechanism is needed for granular set operations where
particular slices should be included or excluded only. So, to make life
easier, a few pseudo-slices are automatically defined:
- "DEFn"
- The union of all user-defined slices at exactly level n (0
<= n <= oo).
- "UNDEFn"
- The union of all non-user-defined slices at exactly
level n (0 <= n <= oo). This actually is just
"!DEFn".
- "DEF"
- The union of all user-defined slices at all levels,
beginning at level 1. This actually is the union of all
"DEFn" slices.
- "UNDEF"
- The union of all non-user-defined slices at
all levels, beginning with 1. This actually is just
"!DEF".
- "ALL"
- The whole file. This actually is just "UNDEF0",
because at level 0 there are no user defined slices, so all is
undefined.
- NAME"@"
- This is the slice NAME minus the union of all
"DEFn" slices with min(NAME) <= n <= oo. Here min(NAME) is
the lowest level plus one where NAME ever occurred. You can read
this as ``NAME without all other slices at higher levels which overwrite
it''. This sounds a little bit crazy, but actually is the most important
construct. Try to understand it or your slice terms become very
complicated.
OPTIONS¶
- [-y outputpolicy]
- This flag changes output policy depending on events:
"u" when an undefined set is encountered, "w" for an
unmatched wildcard set, "z" when output is empty and
"s" if it only consists of whitespace characters. Each letter is
followed by a digit telling which action is bound to such events: 0 to
ignore such events, 1 to display a warning message and continue, 2 to skip
concerned file and continue, and 3 to abort with an error message.
This flag consists of one or more events specifications, and default is
"u0w0s0z0".
- [-o
sliceterm:outputfile[@chmodcmd][# outputpolicy]
..]
- This redirects the output to a file. Usually the whole file
will be send to "STDOUT" (same as "ALL:-"). You can
use this option more than once to output to more than one file
while the corresponding sliceterm determines which output data will
be included into each output file.
The optional chmodcmd string is intended for specifying options for
the chmod command, which is applied to outputfile after
writing. For instance use ``"a+r"'' to make sure the file is
readable by a webserver of ``"u+x"'' to create a file with the
execution bit set (usually used for SSI files on a webserver with the
"XBitHack" option available).
The optional outputpolicy string allows changing output policy for
only this output file without changing its global meaning. See above for
information on output policy.
Be careful here: When you use parenthesis or asterisks inside
sliceterm you have to make sure it is really passed to slice
this way, i.e. usually you have to escape these characters from
interpolation by the used shell. Do this either by adding backslashes in
front of these characters or just surround the complete option argument
with single quotes ('').
- -v
- This sets verbose mode where some processing information
will be given on the console for debugging purpose.
- -V
- Displays the version identification string.
- -h
- Displays the usage page.
SPECIAL FEATURE¶
Sometimes it can be very useful to be able to provide command line options
directly within the input file, for instance to setup one or more
-o
options. For this
slice recognizes lines of the form
%!slice OPTIONS
in the input file and automatically adds OPTIONS to the argument line options.
These lines have to start in column 0.
Example:
%!slice -oTOC:contents.txt
EXAMPLE¶
Assume the following simple multi-language article file
article.src,
written in HTML:
<html>
<head>
<title>[EN:Titlepage:][DE:Titelseite:]</title>
</head>
<body>
<center>
<h1>[EN:The Title itself:][DE:Der Titel selbst:]</h1>
</center>
<blockquote>
[EN:...English Abstract...:]
[DE:...Deutsche Zusammenfassung...:]
</blockquote>
[EN:...English Text...:]
[DE:...Deutscher Text...:]
</body>
</html>
The command
slice -o ENuUNDEF:article.html.en -o DEuUNDEF:article.html.de
then creates the following to files:
- article.html.en:
-
<html>
<head>
<title>Titlepage</title>
</head>
<body>
<center>
<h1>The Title itself</h1>
</center>
<blockquote>
...English Abstract...
</blockquote>
...English Text...
</body>
</html>
- article.html.de:
-
<html>
<head>
<title>Titelseite</title>
</head>
<body>
<center>
<h1>Der Titel selbst</h1>
</center>
<blockquote>
...Deutsche Zusammenfassung...
</blockquote>
...Deutscher Text...
</body>
</html>
RESTRICTION¶
The current implementation only handles anonymous end delimiters
``":]"'' correct in clear cases where no mis-interpretation is
possible, i.e. when no overlapping occurs. For instance in
...[A:...[B:...:A]...:]...
the end delimiter is not correctly assign to the `B' slice. So, be careful when
using anonymous end delimiters in overlapping situations. Pure stacking like
...[A:...[B:...:]...:]...
is allowed and handled correctly, but only when you interpret this as
...[A:...[B:...:B]...:A]...
COPYRIGHT¶
Copyright (c) 1997-2002 Ralf S. Engelschall.
Copyright (c) 1999-2002 Denis Barbier.
SEEALSO¶
Slice Home:
http://www.engelschall.com/sw/slice/
AUTHORS¶
Ralf S. Engelschall
rse@engelschall.com
www.engelschall.com
Denis Barbier
barbier@engelschall.com