Process Help PICREC - copy one file to another using expressions

 

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• Introduction

• Files, Fields and Parameters

• Notes

• Example

• Errors

Introduction

Writes records to an output file if the records in the input file match the given input expressions.

Expression Syntax

An expression may be either a relational expression or a pattern matching expression.

In the following text all keywords are capitalized.  When running PICREC, any keyword may be entered in either uppercase or lowercase and abbreviated to its first three (or more) characters.

Relational Expressions

The syntax of a relational expression is:

	[FIELD]	<fieldname>	<operator>	[CONSTANT]	<value>
or	[FIELD]	<fieldname>	<operator>	[FIELD]	<fieldname>
or	[CONSTANT]	<value>	<operator>	[FIELD]	<fieldname>

 

The keywords FIELD and CONSTANT are optional, and need only be specified where necessary to avoid confusion (e.g. "ROCKTYPE=FIELD T2" or ROCKTYPE=CONSTANT T2").

Any of the six relational operators listed below may be used.

>	Greater than
>=	Greater than or equal to
=	Equal to
<	Less than
<=	Less than or equal to
<>	Not equal to

Pattern Matching

The syntax of a pattern matching expression is:

<fieldname>    MATCHES    [REGEXP]    <pattern>

If the keyword REGEXP is missing, a "pattern" may consist of literal characters to be matched, or one of the following elements.

?	Any single character
*	Wildcard.  A group of zero or more characters
[...]	Any one of the characters enclosed in the square brackets.  The short hand notation "a-z" means any lowercase letter; refer to the examples below for more details.
[^...]	Any character except one of these

 

The special meaning of a character (e.g. "*") is lost if the character is preceded by "\", hence the match a literal "*", use "\*".  Quotes (double or single) may be used to enclose patterns if desired.

If the keyword "REGEXP" is used, the pattern specifies a full regular expression.  Regular expressions allow advanced users to make more complex selections than are possible by using the pattern elements specified above.

A regular expression in PICDIR may contain the following elements.

%	Matches the beginning of the file or field name
$	Matches the end of the file or field name
*	Zero or more occurrences of the preceding pattern element.
?	As above
[...]	As above
[^...]	As above

Concatenation of Expressions

The result of a pattern matching expression is either TRUE or FALSE.  Any result may be inverted by preceding the expression by the keyword "NOT" (e.g. "NOT BHID MATCHES RHD*").  Two expressions may be joined together by "AND" or "OR" operators.  The result is another expression.  The "AND" operator has higher precedence than "OR".  Parentheses (brackets) may be used to override the normal order of evaluation of expressions.

Disambiguating Values

Some text strings are interpreted by PICREC as being a keyword or operator. For example, "CON" is used to represent a "CONSTANT" keyword. This can cause problems if the same string is detected within variable values. For example, STRAT="CONCHA" will generate a parser error as a constant keyword ("CON") is detected but cannot be processed using the following data.

In this situation, you can disambiguate values by prefixing them with a forward slash. Following the above, example, you could use the expression STRAT="/CONCHA" (or even STRAT=/CONCHA as the value contains no spaces).

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Files, Fields and Parameters

Input Files

Name	Description	I/O Status	Required	Type
IN	The name of the file from which records are to be selected.	Input	Yes	Table
FIELDLST	Optional file to specify fields to output.	Input	No	Undefined

Output Files

Name	I/O Status	Required	Type	Description
OUT	Output	Yes	Undefined	The name of the file to which selected records are to be written.

Fields

Name	Description	Source	Required	Type	Default
F1	The name of the first field to be transferred from the input file to the output file. If no fields are explicitly named, all fields are copied. You may only apply relational and pattern matching tests to fields that are to appear in the output file.	IN	No	Any	Undefined
F2	Second field to be copied.	IN	No	Any	Undefined
F3	Third field to be copied.	IN	No	Any	Undefined
F4	Fourth field to be copied.	IN	No	Any	Undefined
F5	Fifth field to be copied.	IN	No	Any	Undefined
FIELDNAM	Field in FIELDLST that holds the names of the data fields to output in OUT.	FIELDLST	No	Character	Undefined

Parameters

Name	Description	Required	Default	Range	Values
APPEND	If set to 1 then selected records will be appended to the OUT file, provided it exists and has the same fields as the input file (0).	No	0	0,1	0,1

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Notes

Placing "\" before a fieldname avoids the fieldname being interpreted as an OPERATOR or a KEYWORD. This is useful when fieldnames or other text elements start (i.e. the first two or three characters, depending the operator or keyword) with letters matching OPERATOR or KEYWORD names, this includes for example:

• MAT (MATCHES)

• REG (REGEXP)

• AND

• OR

• NOT

• FIE (FIELD)

• CON (CONSTANT)

This can be demonstrated by means the following example. Here, the test using the following syntax will fail with an error, as the first three letters of the fieldname i.e. 'MAT' are interpreted as the keyword MATCHES:

TEST> FIELD MATGC="LSO" END

When written as follows, it works as expected:

TEST> FIELD \MATGC="LSO" END

This principle isn't restricted to field names, but applies equally to text within instructions. For example, the following instruction will fail to complete:

TEST> DEVFILE MATCHES “reg*” END

This is because “reg” is interpreted as “regexp”.

The following statement completes successfully, however, as the "\" escape character ensures the following text is interpreted literally:

TEST> DEVFILE MATCHES “\reg*” END

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Example

1.	Select records from a file where BHID values start with the letters "RDH", or the field XCOLLAR is between 10200 and 11200:
	TEST>BHID MATCHES "RDH*" OR TEST>XCOLLAR>=10200 AND XCOLLAR<=11200 TEST>END
2.	Select records where the contents of field "Au1" is greater than the contents of field "Au2":
	TEST>Au1 > Au2 END
3.	Select records where the field LOG contains both codes "Cu" and "Pb".
	TEST>LOG MATCHES *[cC][uU]*[pP][bB]* OR TEST>LOG MATCHES *[pP][bB]*[cC][uU]* END
	Note that "[cC][uU]" will match "cu", "cU", "Cu" or "CU".
4.	Select records where CODE is five characters long, but does NOT end in 3 or 4.
	TEST>CODE MATCHES ????[^34] END alternatively, one could specify the following: TEST>CODE MATCHES ????? AND NOT CODE MATCHES *[34] END
5.	Select all records where ROCKCODE = 7, and BHID is DDH034, DDH147 or DDH136.
	TEST>ROCKCODE=7 AND (BHID=DDH034 OR TEST>BHID=DDH147 OR BHID=DDH136) END
	Note that parentheses are required here, since by the default the expressions would be combined as below:
	TEST>(ROCKCODE=7 AND BHID=DDH034) OR TEST>BHID=DDH147 OR BHID=DDH136 END
6.	Select all records where BHID values begin with zero or more spaces, followed by "RDH".
	TEST>BHID MATCHES REGEXP "% *RDH" END
	A full regular expression is required to match possible leading spaces. Note also how quotes are required, since the pattern contains a space.

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Error and Warning Messages

Message	Description	Solution
>>> ERROR: Read error from file ffffffff	Read error from file specified as &IN. Fatal; the process is exited.
>>> ERROR: field aaaaaaaa is too long	Fatal; the process is exited.
>>> WARNING: Cannot append to file ffffffff. A new file will be created	Cannot append fieldnames to the file specified as &OUT. Check the file name given. A new &OUT file will be created.
>>> ERROR: Files have different DDs, cannot append	File specified in pattern matching expression and the file specified as &OUT have different DDs. Fatal; the process is exited.
>>> ERROR: Unexpected execution error	Fatal; the process is exited.
>>> ERROR: Illegal instruction found	Fatal; the process is exited.
>>> SYNTAX ERROR AT " "	Syntax of pattern matching expression is incorrect. Fatal; the process is exited.	Check that fielnames do not start with two or three letters that could be interpreted as keywords (see help above).
>>> ERROR: Incompatible types for " " and " "	Field types are incompatible in relational expression. Fatal; the process is exited.
>>> ERROR: " " MATCHES ... Alphanumeric field required	Alphanumeric field required for pattern matching expression. Fatal; the process is exited.
>>> ERROR: Illegal pattern:	Illegal pattern in pattern matching expression. Fatal; the process is exited.
>>> ERROR: More than nnnnn instructions	Maximum number of expressions is 100. Fatal; the process is exited.

 

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