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Top Forums Shell Programming and Scripting Overwrite & Delete in Text File Post 302132108 by 33junaid on Wednesday 15th of August 2007 10:09:20 AM
Old 08-15-2007
thanks for the reply......the code is working fine.....ur code is :

awk ' { if ( NR == 1 ) { head=substr($0,1,300);} else { last = substr($0,1,300);} arr[i++]=$0; }END{ printf "Header is : %-300s Trailer is : %-300s\n", head, last; for( x=1; x<i-1; x++) { print arr[x] } }' old_file > new_file


The problem remains still the same ......for example if there are 1000 rows, one header and one trailer.......it concatenates hearder and trailer in one line and then copies this along with other 1000 rows to new file.......thus cuasing a lot of I/O........i have millions of records in the file and cannot afford to transfer one million records just for the sake of 2 lines (i.e. header and trailer)................

Before this, i got this code:

awk ' { if ( NR == 1 ) { head=$0 } else { last = $0 } }END{ printf "%-300s %-300s\n", head, last }' old_file > new_file
sed '1d;$d' old_file >> new_file

the above code has the same problem that it appends all the data rows................pls note that output is coming fine in both cases but I am concerned about the performance................all we need to do is:

1-Get header in old file (say string1)
2-Get trailer in old fine (say string2)
3-concatenate string1 and string2 (say the result is string3)
4-update the header in old file with string3
5-delete the trailer in old file.

Thanks....
 

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Jifty::Action::Record(3pm)				User Contributed Perl Documentation				Jifty::Action::Record(3pm)

NAME
Jifty::Action::Record -- An action tied to a record in the database. DESCRIPTION
Represents a web-based action that is a create, update, or delete of a Jifty::Record object. This automatically populates the arguments method of Jifty::Action so that you don't need to bother. To actually use this class, you probably want to inherit from one of Jifty::Action::Record::Create, Jifty::Action::Record::Update, or Jifty::Action::Record::Delete. You may need to override the "record_class" method, if Jifty cannot determine the record class of this action. METHODS
record Access to the underlying Jifty::Record object for this action is through the "record" accessor. record_class This method can either be overridden to return a string specifying the name of the record class, or the name of the class can be passed to the constructor. report_detailed_messages If the action returns true for "report_detailed_message", report the message returned by the model classes as the resulting message. For Update actions, Put the per-field message in "detailed_messages" field of action result content. The default is false. new PARAMHASH Construct a new "Jifty::Action::Record" (as mentioned in Jifty::Action, this should only be called by "framework->new_action". The "record" value, if provided in the PARAMHASH, will be used to load the "record"; otherwise, the primary keys will be loaded from the action's argument values, and the "record" loaded from those primary keys. arguments Overrides the "arguments" in Jifty::Action method, to automatically provide a form field for every writable attribute of the underlying "record". This also creates built-in validation and autocompletion methods (validate_$fieldname and autocomplete_$fieldname) for action fields that are defined "validate" or "autocomplete". These methods can be overridden in any Action which inherits from this class. Additionally, if our model class defines canonicalize_, validate_, or autocomplete_ FIELD, generate appropriate an appropriate canonicalizer, validator, or autocompleter that will call that method with the value to be validated, canonicalized, or autocompleted. "validate_FIELD" should return a (success boolean, message) list. "autocomplete_FIELD" should return a the same kind of list as Jifty::Action::_autocomplete_argument "canonicalized_FIELD" should return the canonicalized value. possible_columns Returns the list of columns objects on the object that the action can update. This defaults to all of the "containers" or the non-"private", non-"virtual" and non-"serial" columns of the object. possible_fields Returns the list of the "possible_columns"' names. Usually at the end names are required, however for subclassing column objects are better, or this method in a subclass turns out to be "map to column" - "filter" - "map to name" chain. take_action Throws an error unless it is overridden; use Jifty::Action::Record::Create, ::Update, or ::Delete SEE ALSO
Jifty::Action, Jifty::Record, Jifty::DBI::Record, Jifty::Action::Record::Create, Jifty::Action::Record::Update, Jifty::Action::Record::Delete LICENSE
Jifty is Copyright 2005-2010 Best Practical Solutions, LLC. Jifty is distributed under the same terms as Perl itself. perl v5.14.2 2011-02-21 Jifty::Action::Record(3pm)
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