search++(1) General Commands Manual search++(1)
NAME
search++ - SWISH++ searcher
SYNOPSIS
search++ [ options ] query
DESCRIPTION
search++ is the SWISH++ searcher. It searches a previously generated
index for the words specified in a query. In addition to running from
the command-line, it can run as a daemon process functioning as a
``search++ server.''
QUERY INPUT
Query Syntax
The formal grammar of a query is:
query: query relop meta
meta
meta: meta_name = primary
primary
meta_name: word
primary: (query)
not meta
word
word*
relop: and
near
not near
or
(empty)
In practice, however, the query is the set of words sought after, possi-
bly restricted to meta data, and possibly combined with the operators
``and,'' ``or,'' ``near,'' ``not,'' and ``not near.'' The asterisk (*)
can be used as a wildcard character at the end of words. Note that an
asterisk and parentheses are shell meta-characters and as such must ei-
ther be escaped (backslashed) or quoted when passed to a shell.
Although syntactically legal, it is a semantic error to have ``near''
just before ``not'' since such queries are nonsensical, e.g.:
mouse near not computer
Queries are evaluated in left-to-right order, i.e., ``and'' has the same
precedence as ``or.'' For more about query syntax, see the EXAMPLES.
Character Mapping and Word Determination
The same character mapping and word determination heuristics used by in-
dex++(1) are used on queries prior to searching.
RESULTS OUTPUT
Result Components
The results are output either in ``classic'' or XML format. In either
case, the components of the results are:
rank An integer from 1 to 100.
path-name The relative path to where the file was originally indexed.
file-size The file's size in bytes.
file-title If the file is of a format that can have titles (HTML,
XHTML, LaTeX, mail, or Unix manual pages) and the title was
extracted, then file-title is its title; otherwise, it is
its filename.
Classic Results Format
The ``classic'' results format is plain text as:
rank path-name file-size file-title
It can be parsed easily in Perl with:
($rank,$path,$size,$title) = split( / /, $_, 4 );
(The separator can be changed via the -R or --separator options or the
ResultSeparator variable.)
Prior to results lines, comment lines may also appear containing addi-
tional information about the query results. Comment lines are in the
format of:
# comment-key: comment-value
The keys and values are:
ignored: stop-words The list of stop-words (separated by
spaces) ignored in the query.
not found: word The word was not found in the index.
results: result-count The total number of results.
XML Results Format
The XML results format is given by the DTD:
<!ELEMENT SearchResults (IgnoredList?, ResultCount, ResultList?)>
<!ELEMENT IgnoredList (Ignored+)>
<!ELEMENT Ignored (#PCDATA)>
<!ELEMENT ResultCount (#PCDATA)>
<!ELEMENT ResultList (File+)>
<!ELEMENT File (Rank, Path, Size, Title)>
<!ELEMENT Rank (#PCDATA)>
<!ELEMENT Path (#PCDATA)>
<!ELEMENT Size (#PCDATA)> <!ELEMENT Title (#PCDATA)>
and by the XML schema located at:
http://homepage.mac.com/pauljlucas/software/swish/SearchResults/SearchResults.xsd
For example:
<?xml version="1.0" encoding="us-ascii"?>
<!DOCTYPE SearchResults SYSTEM
"http://homepage.mac.com/pauljlucas/software/swish/SearchResults.dtd">
<SearchResults
xmlns="http://homepage.mac.com/pauljlucas/software/swish/SearchResults"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://homepage.mac.com/pauljlucas/software/swish/SearchResults
SearchResults.xsd">
<IgnoredList>
<Ignored>stop-word</Ignored>
...
</IgnoredList>
<ResultCount>42</ResultCount>
<ResultList>
<File>
<Rank>rank</Rank>
<Path>path-name</Path>
<Size>file-size</Size>
<Title>file-title</Title>
</File>
...
</ResultList>
</SearchResults>
RUNNING AS A DAEMON PROCESS
Description
search++ can alternatively run as a daemon process (via either the -b or
--daemon-type options or the SearchDaemon variable) functioning as a
``search++ server'' by listening to a Unix domain socket (specified by
either the -u or --socket-file options or the SocketFile variable), a
TCP socket (specified by either the -a or --socket-address options or
the SocketAddress variable), or both. Unix domain sockets are preferred
for both performance and security. For search-intensive applications,
such as a search engine on a heavily used web site, this can yield a
large performance improvement since the start-up cost (fork(2), exec(2),
and initialization) is paid only once.
If the process was started with root privileges, it will give them away
immediately after initialization and before servicing any requests.
Clients and Requests
Search clients connect to a daemon via a socket and send a query in the
same manner as on the command line (including the first word being
``search++''). The only exception is that shell meta-characters must
not be escaped (backslashed) since no shell is involved. Search results
are returned via the same socket. See the EXAMPLES.
Multithreading
A daemon can serve multiple query requests simultaneously since it is
multi-threaded. When started, it ``pre-threads'' meaning that it cre-
ates a pool of threads in advance that service an indefinite number of
requests as a further performance improvement since a thread is not cre-
ated and destroyed per request.
There is an initial, minimum number of threads in the thread pool. The
number of threads grows dynamically when there are more requests than
threads, but not more than a specified maximum to prevent the server
from thrashing. (See the -t, --min-threads, -T, and --max-threads op-
tions or the ThreadsMin or ThreadsMax variables.) If the number of
threads reaches the maximum, subsequent requests are queued until exist-
ing threads become available to service them after completing in-
progress requests. (See either the -q or --queue-size options or the
SocketQueueSize variable.)
If there are more than the minimum number of threads and some remain
idle longer than a specified timeout period (because the number of re-
quests per unit time has dropped), then threads will die off until the
pool returns to its original minimum size. (See either the -O or
--thread-timeout options or the ThreadTimeout variable.)
Restrictions
A single daemon can search only a single index. To search++ multiple
indices concurrently, multiple daemons can be run, each searching its
own index and using its own socket. An index must not be modified or
deleted while a daemon is using it.
OPTIONS
Options begin with either a `-' for short options or a ``--'' for long
options. Either a `-' or ``--'' by itself explicitly ends the options;
however, the difference is that `-' is returned as the first non-option
whereas ``--'' is skipped entirely. Either short or long options may be
used. Long option names may be abbreviated so long as the abbreviation
is unambiguous.
For a short option that takes an argument, the argument is either taken
to be the remaining characters of the same option, if any, or, if not,
is taken from the next option unless said option begins with a `-'.
Short options that take no arguments can be grouped (but the last option
in the group can take an argument), e.g., -Bq511 is equivalent to -B -q
511.
For a long option that takes an argument, the argument is either taken
to be the characters after a `=', if any, or, if not, is taken from the
next option unless said option begins with a `-'.
-?
--help Print the usage (``help'') message and exit.
-aa
--socket-address=a When running as a daemon, the address, a, to listen
to for TCP requests. (Default is all IP addresses
and port 1967.) The address argument is of the
form:
[ host : ] port
that is: an optional host and colon followed by a
port number. The host may be one of a host name, an
IP address, or the * character meaning ``any IP ad-
dress.'' Omitting the host and colon also means
``any IP address.''
-bt
--daemon-type=t Run as a daemon process. (Default is not to.) The
type, t, is one of:
none Same as not specifying the option at all.
(This does not purport to be useful, but
rather consistent with the types that can be
specified to the SearchDaemon variable.)
tcp Listen on a TCP socket (see the -a option).
unix Listen on a Unix domain socket (see the -u
option).
both Listen on both.
By default, if executed from the command-line,
search++ appears to return immediately; however, it
has merely detached from the terminal and put itself
into the background. There is no need to follow the
command with an `&'.
-B
--no-background When running as a daemon process, do not detach from
the terminal and run in the background. (Default
does.)
The reason not to run in the background is so a
wrapper script can see if the process dies for any
reason and automatically restart it.
This option is implied by the -X or --launchd op-
tions.
-cf
--config-file=f The name of the configuration file, f, to use. (De-
fault is swish++.conf in the current directory.) A
configuration file is not required: if none is spec-
ified and the default does not exist, none is used;
however, if one is specified and it does not exist,
then this is an error.
-d
--dump-words Dump the query word indices to standard output and
exit. Wildcards are not permitted.
-D
--dump-index++ Dump the entire word index to standard output and
exit.
-Ff
--format=f The format, f, search results are output in. The
format is either classic or XML. (Default is clas-
sic.)
-Gs
--group=s The group, s, to switch the process to after start-
ing and only if started as root. (Default is no-
body.)
-if
--index-file=f The name of the index file, f, to use. (Default is
swish++.index in the current directory.)
-mn
--max-results=n The maximum number of results, n, to return. (De-
fault is 100.)
-M
--dump-meta Dump the meta-name index to standard output and
exit.
-nn
--near=n The maximum number of words apart, n, two words can
be to be considered ``near'' each other in queries
using near. (Default is 10.)
-os
--socket-timeout=s The number of seconds, s, a sarch client has to com-
plete a query request before the socket connection
is closed. (Default is 10.) This is to prevent a
client from connecting, not completing a request,
and causing the thread servicing the request to wait
forever.
-Os
--thread-timeout=s The number of seconds, s, until an idle spare thread
dies while running as a daemon. (Default is 30.)
-pn
--word-percent=n The maximum percentage, n, of files a word may occur
in before it is discarded as being too frequent.
(Default is 100.) If you want to keep all words re-
gardless, specify 101.
-Pf
--pid-file=f The name of the file to record the process ID of
search++ if running as a daemon. (Default is none.)
-qn
--queue-size=n The maximum number of socket connections to queue.
(Default is 511.)
-rn
--skip-results=n The initial number of results, n, to skip. (Default
is 0.) Used in conjunction with -m or --max-re-
sults, results can be returned in ``pages.''
-Rs
--separator=s The classic result separator string. (Default is "
".)
-s
--stem-words Perform stemming (suffix stripping) on words during
the search. Words that end in the wildcard charac-
ter are not stemmed. (Default is no.)
-S
--dump-stop Dump the stop-word index to standard output and
exit.
-tn
--min-threads=n Minimum number of threads to maintain while running
as a daemon.
-Tn
--max-threads=n Maximum number of threads to allow while running as
a daemon.
-uf
--socket-file=f The name of the Unix domain socket file to use while
running as a daemon. (Default is
/tmp/search.socket.)
-Us
--user=s The user, s, to switch the process to after starting
and only if started as root. (Default is nobody.)
-V
--version Print the version number of SWISH++ to standard out-
put and exit.
-wn[,c]
--window=n[,c] Dump a ``window'' of at most n lines around each
query word matching c characters. Wildcards are not
permitted. (Default for c is 0.) Every window ends
with a blank line.
-X
--launchd If run as a daemon process, cooperate with Mac OS
X's launchd(8) by not ``daemonizing'' itself since
launchd(8) handles that. This option implies the -B
or --no-background options.
This option is available only under Mac OS X, should
be used only for version 10.4 (Tiger) or later, and
only when search++ will be started via launchd(8).
CONFIGURATION FILE
The following variables can be set in a configuration file. Variables
and command-line options can be mixed, the latter taking priority.
Group Same as -G or --group
IndexFile Same as -i or --index-file
LaunchdCooperation Same as -X or --launchd
PidFile Same as -P or --pid-file
ResultSeparator Same as -R or --separator
ResultsFormat Same as -F or --format
ResultsMax Same as -m or --max-results
SearchBackground Same as -B or --no-background
SearchDaemon Same as -b or --daemon-type
SocketAddress Same as -a or --socket-address
SocketFile Same as -u or --socket-file
SocketQueueSize Same as -q or --queue-size
SocketTimeout Same as -o or --socket-timeout
StemWords Same as -s or --stem-words
ThreadsMax Same as -T or --max-threads
ThreadsMin Same as -t or --min-threads
ThreadTimeout Same as -O or --thread-timeout
User Same as -U or --user
WordFilesMax Same as -f or --word-files
WordPercentMax Same as -p or --word-percent
WordsNear Same as -n or --near
EXAMPLES
Simple Queries
The query:
computer mouse
is the same as and short for:
computer and mouse
(because ``and'' is implicit) and would return only those documents that
contain both words. The query:
cat or kitten or feline
would return only those documents regarding cats. The query:
mouse and computer or keyboard
is the same as:
(mouse and computer) or keyboard
(because queries are evaluated left-to-right) in that they will both re-
turn only those documents regarding either mice attached to a computer
or any kind of keyboard. However, neither of those is the same as:
mouse and (computer or keyboard)
that would return only those documents regarding mice (including the ro-
dents) and either a computer or a keyboard.
Queries Using Wildcards
The query:
comput*
would return only those documents that contain words beginning with
``comput'' such as ``computation,'' ``computational,'' ``computer,''
``computerize,'' ``computing,'' and others. Wildcarded words can be
used anywhere ordinary words can be. The query:
comput* (medicine or doctor*)
would return only those documents that contain something about computer
use in medicine or by doctors.
Queries Using ``not''
The query:
mouse or mice and not computer*
would return only those documents regarding mice (the rodents) and not
the kind attached to a computer.
Queries Using ``near''
Using ``near'' is the same as using ``and'' except that it not only re-
quires both words to be in the documents, but that they be near each
other, i.e., it returns potentially fewer documents than the correspond-
ing ``and'' query. The query:
computer near mouse
would return only those documents where both words are near each other.
They query:
mouse near (computer or keyboard)
is the same as:
(mouse near computer) or (mouse near keyboard)
i.e., ``near'' gets distributed across parenthesized subqueries.
Queries Using ``not near''
Using ``not near'' is the same as using ``and not'' except that it al-
lows the right-hand side words to be in the documents, just not near the
left-hand side words, i.e., it returns potentially more documents than
the corresponding ``and not'' query. Of course the word(s) on the
right-hand side need not be in the documents at all, i.e., they would be
considered ``infinitely far'' apart. The query:
mouse or mice not near computer*
would return only those documents regarding mice (the rodents) more ef-
fectively than the query:
mouse or mice and not computer*
because the latter would exclude documents about mice (the rodents)
where computers just so happened to be mentioned in the same documents.
Queries Using Meta Data
The query:
author = hawking
would return only those documents whose author attribute contains
``hawking.'' The query:
author = hawking radiation
would return only those documents regarding radiation whose author at-
tribute contains ``hawking.'' The query:
author = (stephen hawking)
would return only those documents whose author is Stephen Hawking. The
query:
author = (stephen hawking) or (black near hole*)
would return only those documents whose author is Stephen Hawking or
that contain the word ``black'' near ``hole'' or ``holes'' regardless of
the author. Note that the second set of parentheses are necessary oth-
erwise the query would have been the same as:
(author = (stephen hawking) or black) near hole*
that would have additionally required both ``stephen'' and ``hawking''
to be near ``hole'' or ``holes.''
Sending Queries to a Search Daemon
To send a query request to a sarch daemon using Perl, first open the
socket and connect to the daemon (see [Wall], pp. 439-440):
use Socket;
$SocketFile = '/tmp/search.socket';
socket( SEARCH, PF_UNIX, SOCK_STREAM, 0 ) or
die "can not open socket: $!\n";
connect( SEARCH, sockaddr_un( $SocketFile ) ) or
die "can not connect to \"$SocketFile\": $!\n";
Autoflush must be set for the socket filehandle (see [Wall], p. 781),
otherwise the server thread will hang since I/O buffering will wait for
the buffer to fill that will never happen since queries are short:
select( (select( SEARCH ), $| = 1)[0] );
Next, send a query request (beginning with the word ``search++'' and any
options just as with a command-line) to the daemon via the socket file-
handle making sure to include a trailing newline since the server reads
an entire line of input (so therefore it looks and waits for a newline):
$query = 'mouse and computer';
print SEARCH "search++ $query\n";
Finally, read the results back and print them:
print while <SEARCH>;
close( SEARCH );
EXIT STATUS
Exits with one of the values given below:
0 Success.
1 Error in configuration file.
2 Error in command-line options.
40 Unable to read index file.
50 Malformed query.
51 Attempted ``near'' search++ without word-position data.
60 Could not write to PID file.
61 Host or IP address is invalid or nonexistent.
62 Could not open a TCP socket.
63 Could not open a Unix domain socket.
64 Could not unlink(2) a Unix domain socket file.
65 Could not bind(3) to a TCP socket.
66 Could not bind(3) to a Unix domain socket.
67 Could not listen(3) to a TCP socket.
68 Could not listen(3) to a Unix domain socket.
69 Could not select(3).
70 Could not accept(3) a socket connection.
71 Could not fork(2) child process.
72 Could not change directory to /.
73 Could not create thread.
74 Could not create thread key.
75 Could not detach thread.
76 Could not initialize thread condition.
77 Could not initialize thread mutex.
78 Could not switch to user.
79 Could not switch to group.
CAVEATS
1. Stemming can be done only when searching through and index of files
that are in English because the Porter stemming algorithm used only
stems English words.
2. When run as a daemon using a TCP socket, there are no security re-
strictions on who may connect and search++. The code to implement
domain and IP address restrictions isn't worth it since such things
are better handled by firewalls and routers.
3. XML output can currently only be obtained for actual search results
and not word, index, meta-name, or stop-word dumps.
FILES
swish++.conf default configuration file name
swish++.index default index file name
SEE ALSO
index++(1), perlfunc(1), exec(2), fork(2), unlink(2), accept(3),
bind(3), listen(3), select(3), swish++.conf(5), launchd(8), searchmoni-
tor(8)
Tim Bray, et al. Extensible Markup Language (XML) 1.0, February 10,
1998.
Bradford Nichols, Dick Buttlar, and Jacqueline Proulx Farrell. Pthreads
Programming, O'Reilly & Associates, Sebastopol, CA, 1996.
M.F. Porter. ``An Algorithm For Suffix Stripping,'' Program, 14(3),
July 1980, pp. 130-137.
W. Richard Stevens. Unix Network Programming, Vol 1, 2nd ed., Prentice-
Hall, Upper Saddle River, NJ, 1998.
Larry Wall, et al. Programming Perl, 3rd ed., O'Reilly & Associates,
Inc., Sebastopol, CA, 2000.
AUTHOR
Paul J. Lucas <pauljlucas@mac.com>
SWISH++ June 16, 2005 search++(1)
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