agrep.1

agrep

.TH AGREP l "Jan 17, 1992"
.SH NAME
agrep \- search a file for a string or regular expression, with approximate matching capabilities
.SH SYNOPSIS
.B agrep
[
.B \-#cdehiklnpstvwxBDGIS
]
.I pattern 
[ -f
.I patternfile 
]
[
.IR filename ".\|.\|. ]" 
.SH DESCRIPTION
.B agrep
searches the input
.IR filenames
(standard input is the default, but see a warning under LIMITATIONS) 
for records containing strings which either 
\fIexactly\fP or \fIapproximately\fP match a pattern.  
A record is by default a line, but it can be defined differently using
the -d option (see below).
Normally, each record found is copied to the standard output.
Approximate matching allows finding records that contain the pattern 
with several errors including substitutions, insertions, and
deletions.
For example, Massechusets matches Massachusetts with two errors
(one substitution and one insertion).  Running 
.B agrep
-2 Massechusets foo outputs all lines in foo containing any string with
at most 2 errors from Massechusets.
.LP
.B agrep 
supports many kinds of queries including 
arbitrary wild cards, sets of patterns, and in general,
regular expressions.
See PATTERNS below.
It supports most of the options supported by the 
.B grep
family plus several more (but it is not 100% compatible with grep).
For more information on the algorithms used by agrep see
Wu and Manber, 
"Fast Text Searching With Errors,"
Technical report #91-11, Department of Computer Science, University
of Arizona, June 1991 (available by anonymous ftp from cs.arizona.edu
in agrep/agrep.ps.1), and
Wu and Manber,
"Agrep -- A Fast Approximate Pattern Searching Tool",
To appear in USENIX Conference 1992 January (available by anonymous ftp
from cs.arizona.edu in agrep/agrep.ps.2).
.LP
As with the rest of the \fBgrep\fP family, the characters
.RB ` $ ',
.RB `^ ',
.RB ` \(** ',
.RB ` [ ' ,
.RB ` ] ' ,
.RB ` \s+2^\s0 ',
.RB ` | ',
.RB ` ( ',
.RB ` ) ',
.RB ` ! ',
and
.RB ` \e '
can cause unexpected results when included in the
.IR pattern ,
as these characters are also meaningful
to the shell.  To avoid these problems, one should always enclose the entire
pattern argument in single quotes, i.e., 'pattern'.
Do not use double quotes (").
.LP
When
.B agrep
is applied to more than one input
file, the name of the file is displayed
preceding each line which matches
the pattern.  The filename is not displayed
when processing a single
file, so if you actually want the filename
to appear, use
.B /dev/null
as a second file in the list.
.SH OPTIONS
.TP
.B \-\fI#\fP
\fI#\fP is a non-negative integer (at most 8)
specifying the maximum number of errors
permitted in finding the approximate matches (defaults to zero).
Generally, each insertion, deletion, or substitution counts as one error.
It is possible to adjust the relative cost of insertions,
deletions and substitutions (see -I -D and -S options).
.TP
.B \-c
Display only the count of matching records.
.TP
.B \-d "'\fIdelim\fP'"
Define \fIdelim\fP to be the separator between two records.
The default value is '$', namely a record is by default
a line.
\fIdelim\fP can be a string of size at most 8
(with possible use of ^ and $), but not
a regular expression.
Text between two \fIdelim\fP's, before the first \fIdelim\fP,
and after the last \fIdelim\fP is considered as one record.
For example, -d '$$' defines paragraphs as records and -d '^From\ '
defines mail messages as records.
.B agrep
matches each record separately.
This option does not currently work with regular expressions.
.TP
.BI \-e " pattern"
Same as a simple
.I pattern
argument, but useful when the
.I pattern
begins with a
.RB ` \- '.
.TP
.BI \-f " patternfile"
.I patternfile 
contains a set of (simple) patterns.
The output is all lines that match at least one of the patterns in 
.I patternfile.
Currently, the \-f option works only for exact match and for simple
patterns (any meta symbol is interpreted as a regular character);
it is compatible only with \-c, \-h, \-i, \-l, \-s, \-v, \-w, and \-x options.
see LIMITATIONS for size bounds.
.TP
.B \-h
Do not display filenames.
.TP
.B \-i
Case-insensitive search \(em e.g., "A" and "a" are considered equivalent.
.TP
.B \-k
No symbol in the pattern is treated as a meta character. 
For example, agrep -k 'a(b|c)*d' foo will find  
the occurrences of a(b|c)*d in foo whereas agrep 'a(b|c)*d' foo
will find substrings in foo that match the regular expression 'a(b|c)*d'.
.TP
.B \-l
List only the files that contain a match.
This option is useful for looking for files containing a certain pattern.
For example, " agrep -l 'wonderful'  * " will list the names of those
files in current directory that contain the word 'wonderful'.
.TP
.B \-n
Each line that is printed is prefixed by its record number in the file.
.TP
.B \-p
Find records in the text that contain a supersequence of the pattern.
For example,
\fB agrep \-p DCS foo
will match "Department of Computer Science."
.TP
.B \-s   
Work silently, that is, display nothing except error messages.
This is useful for checking the error status.
.TP
.B \-t   
Output the record starting from the end of 
.I delim
to (and including) the next
.I delim.
This is useful for cases where 
.I delim
should come at the end of the record.
.TP
.B \-v
Inverse mode \(em display only those records that
.I do not
contain the pattern.
.TP
.B \-w
Search for the pattern as a word \(em i.e., surrounded by non-alphanumeric
characters.  The non-alphanumeric 
.B must
surround the match;  they cannot be counted as errors.
For example, 
.B agrep
-w -1 car will match cars, but not characters.
.TP
.B \-x
The pattern must match the whole line.
.TP
.B \-y
Used with \-B option. When \-y is on, agrep will always 
output the best matches without giving a prompt.
.TP
.B \-B
Best match mode.
When \-B is specified and no exact matches are found, agrep
will continue to search until the closest matches (i.e., the ones
with minimum number of errors)
are found, at which point the following message will be shown:
"the best match contains x errors, there are y matches, output them? (y/n)"
The best match mode is not supported for standard input, e.g.,
pipeline input.
When the \-#, \-c, or \-l options are specified, the \-B option is ignored.
In general, \-B may be slower than \-#, but not by very much.
.TP
.B \-D\fIk\fP
Set the cost of a deletion to \fIk\fP (\fIk\fP is a positive integer).
This option does not currently work with regular expressions.
.TP
.B \-G
Output the files that contain a match.
.TP
.B \-I\fIk\fP
Set the cost of an insertion to \fIk\fP (\fIk\fP is a positive integer).
This option does not currently work with regular expressions.
.TP
.B \-S\fIk\fP
Set the cost of a substitution to \fIk\fP (\fIk\fP is a positive integer).
This option does not currently work with regular expressions.
.ne 4
.SH PATTERNS
.LP
\fIagrep\fP 
supports a large variety of patterns, including simple
strings, strings with classes of characters, sets of strings, 
wild cards, and regular expressions.
.TP
\fBStrings\fP
any sequence of characters, including the special symbols
`^' for beginning of line and `$' for end of line.
The special characters listed above (
.RB ` $ ',
.RB `^ ',
.RB ` \(** ',
.RB ` [ ' ,
.RB ` \s+2^\s0 ',
.RB ` | ',
.RB ` ( ',
.RB ` ) ',
.RB ` ! ',
and
.RB ` \e '
) should be preceded by `\\' if they are to be matched as regular
characters.  For example, \\^abc\\\\ corresponds to the string ^abc\\,
whereas ^abc corresponds to the string abc at the beginning of a
line.
.TP
\fBClasses of characters\fP
a list of characters inside [] (in order) corresponds to any character
from the list.  For example, [a-ho-z] is any character between a and h
or between o and z.  The symbol `^' inside [] complements the list.
For example, [^i-n] denote any character in the character set except
character 'i' to 'n'.
The symbol `^' thus has two meanings, but this is consistent with
egrep.
The symbol `.' (don't care) stands for any symbol (except for the
newline symbol).
.TP
\fBBoolean operations\fP
.B agrep 
supports an `and' operation `;' 
and an `or' operation `,',
but not a combination of both.  For example, 'fast;network' searches
for all records containing both words.
.TP
\fBWild cards\fP
The symbol '#' is used to denote a wild card.  # matches zero or any
number of arbitrary characters.  For example, 
ex#e matches example.  The symbol # is equivalent to .* in egrep.
In fact, .* will work too, because it is a valid regular expression
(see below), but unless this is part of an actual regular expression,
# will work faster. 
.TP
\fBCombination of exact and approximate matching\fP
any pattern inside angle brackets <> must match the text exactly even
if the match is with errors.  For example, <mathemat>ics matches
mathematical with one error (replacing the last s with an a), but
mathe<matics> does not match mathematical no matter how many errors we
allow.
.TP
\fBRegular expressions\fP
The syntax of regular expressions in \fBagrep\fP is in general the same as
that for \fBegrep\fP.  The union operation `|', Kleene closure `*',
and parentheses () are all supported.
Currently '+' is not supported.
Regular expressions are currently limited to approximately 30
characters (generally excluding meta characters).  Some options
(\-d, \-w, \-f, \-t, \-x, \-D, \-I, \-S) do not 
currently work with regular expressions.
The maximal number of errors for regular expressions that use '*'
or '|' is 4.
.SH EXAMPLES
.LP
.TP
agrep -2 -c ABCDEFG foo 
gives the number of lines in file foo that contain ABCDEFG
within two errors.
.TP
agrep -1 -D2 -S2 'ABCD#YZ' foo
outputs the lines containing ABCD followed, within arbitrary
distance, by YZ, with up to one additional insertion
(-D2 and -S2 make deletions and substitutions too "expensive").
.TP
agrep -5 -p abcdefghij /usr/dict/words
outputs the list of all words containing at least 5 of the first 10
letters of the alphabet \fIin order\fR.  (Try it:  any list starting
with academia and ending with sacrilegious must mean something!)
.TP 
agrep -1 'abc[0-9](de|fg)*[x-z]' foo
outputs the lines containing, within up to one error, the string
that starts with abc followed by one digit, followed by zero or more
repetitions of either de or fg, followed by either x, y, or z.
.TP
agrep -d '^From\ ' 'breakdown;internet' mbox
outputs all mail messages (the pattern '^From\ ' separates mail messages
in a mail file) that contain keywords 'breakdown' and 'internet'.
.TP
agrep -d '$$' -1 '<word1> <word2>' foo
finds all paragraphs that contain word1 followed by word2 with one
error in place of the blank.  
In particular, if word1 is the last word in a line and word2
is the first word in the next line, then the space will be
substituted by a newline symbol and it will match.
Thus, this is a way to overcome separation by a newline.
Note that -d '$$' (or another delim which spans more than one line)
is necessary, because otherwise agrep searches
only one line at a time.
.TP
agrep '^agrep' <this manual>
outputs all the examples of the use of agrep in this man pages.
.PD
.SH "SEE ALSO"
.BR ed (1),
.BR ex (1),
.BR grep (1V),
.BR sh (1),
.BR csh (1).
.SH BUGS/LIMITATIONS
Any bug reports or comments will be appreciated! 
Please mail them to [e-mail] or [e-mail]
.LP
Regular expressions do not support the '+' operator (match 1 or more
instances of the preceding token).  These can be searched for by using
this syntax in the pattern:
.sp
.in 1.0i
\&'\fIpattern\fB(\fIpattern\fB)*\fR'
.in
.sp
(search for strings containing one instance of the pattern, followed by 0 or
more instances of the pattern).
.LP
The following can cause an infinite loop:
.B agrep
pattern * > output_file.
If the number of matches is high, they may be deposited in
output_file before it is completely read leading to more matches of
the pattern within output_file (the matches are against the whole
directory).  It's not clear whether this is a "bug" (grep will do the
same), but be warned.
.LP
The maximum size of the 
.I patternfile
is limited to be 250Kb, and the maximum number of patterns
is limited to be 30,000.
.LP
Standard input is the default if no input file is given.
However, if standard input is keyed in directly (as opposed to through
a pipe, for example) agrep may not work for some non-simple patterns.
.LP
There is no size limit for simple patterns.
More complicated patterns are currently limited to approximately 30 characters.
Lines are limited to 1024 characters.
Records are limited to 48K, and may be truncated if they are larger
than that.
The limit of record length can be 
changed by modifying the parameter Max_record in agrep.h.
.SH DIAGNOSTICS
Exit status is 0 if any matches are found,
1 if none, 2 for syntax errors or inaccessible files.
.SH AUTHORS
Sun Wu and Udi Manber, Department of Computer Science, University of
Arizona, Tucson, AZ 85721.  {sw|udi}@cs.arizona.edu.