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107 lines
2.7 KiB
Groff
107 lines
2.7 KiB
Groff
." $Id: regex.1,v 1.2.16.1.2.2 2009/06/18 16:19:38 steve Exp $
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.TH REGEX 1 "$Date: 2009/06/18 16:19:38 $"
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.SH NAME
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regex \- Verify extended regular-expressions.
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.SH SYNOPSIS
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.HP
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.ft B
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regex
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.nh
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\%[-n\ \fIcount\fP]
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\%[-s\ \fIstring\fP]
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\%\fIpattern\fP]
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.hy
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.ft
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.SH DESCRIPTION
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.LP
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This utility validates an extended regular-expression and,
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optionally, matches it against a specified string.
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.LP
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A looping option allows sufficient time to accumulate to permit the
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determination
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of the relative efficiency of, otherwise, equivalent regular-expressions.
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.LP
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Because a downstream LDM uses a extended regular-expression in its
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request for data products from an upstream LDM, it is important that the
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regular expression be efficient. We have documented simple but
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pathological regular expressions from a downstream LDM request that have
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caused the upstream LDM to spend over 99% of its user-time in the execution
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of the regular expressions. We're not making this up.
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.SH OPTIONS
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.TP
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.BI "-n " count
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The number of times to match the regular-expression against the string.
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.TP
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.BI "-s " string
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The string to be matched against the regular-expression.
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.SH OPERAND
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.TP
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.I pattern
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An extended reqular-expression to be compiled and, optionally, compared against
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the argument of the
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.B \-s
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option.
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.SH "STANDARD OUTPUT"
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If the regular-expression is successfully compiled and the
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.B \-s
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option is
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used, then the utility prints "match" or "no match" as appropriate
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to standard output.
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.SH "STANDARD ERROR"
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If the utility is incorrectly invoked or the regular-expression fails to
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compile, then a diagnostic message is written to standard error.
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.SH EXAMPLE
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The regular-expression
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.B [09]$
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is MUCH faster than the regular-expression
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.B .*[09]$
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under Solaris:
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.nf
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.RS +4
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$ time ./regex -n 10000 -s 'xxxxxxxxxxxxxxxxx' '[09]$'
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no match
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real 0m0.014s
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user 0m0.010s <-- NOTE
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sys 0m0.010s
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$ time ./regex -n 10000 -s 'xxxxxxxxxxxxxxxxx' '.*[09]$'
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no match
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real 0m1.870s
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user 0m1.850s <-- NOTE
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sys 0m0.010s
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.fi
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.RE
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.SH "EXIT STATUS"
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.LP
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The following exit values are returned:
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.TP
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0
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Success. Regular-expression successfuly compiled.
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.TP
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1
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Usage error.
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.TP
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2
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Regular-expression error.
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.SH "SEE ALSO"
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For information on extended regular-expressions, see
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.B http://www.opengroup.org/onlinepubs/7908799/xbd/re.html.
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.SH SUPPORT
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.LP
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If you have problems with this program, then you should first examine the
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LDM email archive for similar problems and how they were solved.
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The email archive is available via the following World Wide Web URL:
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.sp
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.RS
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\fBhttp://www.unidata.ucar.edu/software/ldm/\fP
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.RE
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.sp
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If this does not suffice and your site is a member of the Unidata
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program, then send an inquiry via email -- together will all relevant
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information -- to
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.sp
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.RS
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\fBsupport@unidata.ucar.edu\fP
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.RE
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