Danny Fang wrote:
However, I'm not sure how I could rewrite the newly modified column values of
that particular row back into the file - I want to use the particular row which
had its columns modified to be duplicated and appended to the end of the
current file for a specific number of time (adding more rows with the
duplicated rows).
It is considered bad form to write back into a text file since a change
of length of one byte in a record could screw-up the rest of the file.
#!/usr/bin/perl
use strict;
use warnings;
use diagnostics;
##open file for reading
open(INPUTFILE, $inputFile) || die "Cannot open $inputFile \n";
# Is $inputFile tainted? That is, is it hard-coded
# or a user given value. To protect yourself from
# malicious users, use:
open INPUTFILE, "< $inputFile" or die "...";
# If you don't see why, ask yourself what if the
# user gives ">~/.profile" as the $inputFile?
# What if he gives "rm -fr * |"?
@fileRecs = <INPUTFILE>;
$totalRecs = scalar(@fileRecs)-1;
print "Total records in $inputFile is $totalRecs \n";
##open file for writting output
open(OUTFILE, ">$inputFile.tmp") || die "Cannot open $inputFile.tmp \n";
$secondRow = $fileRecs[2];
print "BEGINNING -- secondRow = $secondRow \n";
@secondRowRec = split("|", $secondRow);
$secondRowRec[2]="AAAA";
$secondRowRec[3]="BBBBB";
# Now put the record back together.
$secondRow = join( "|", @secondRowRec );
$fileRecs[2] = $secondRow;
print "\$secondRowRec[2] = $secondRowRec[2] and \$secondRowRec[3]=$secondRowRec[3]
\n";
print "\$secondRow is now $secondRow \n";
$diffOfNewRec = 4000 - $totalRecs;
print "Need to produce additional $diffOfNewRec \n";
#making a backup copy
`cp $inputFile $inputFile.tmp`;
# Bad idea. You have just opened $inputFile.tmp for writing. Try:
use File::Copy qw( copy move );
copy( $inputFile, "$inputFile.bak" );
## I'm need help here !! Not sure how I could re-join the elements modified back into the array containing that particular row and append it to the end of the file
##
print OUTFILE for ($i=0;$i<$diffOfNewRec; $i++){
print OUTFILE "$secondRow\n";
}
close OUTFILE;
for my $rec ( @fileRecs ){
print OUTFILE, $rec or die "cannot write to output: $!";
}
# To speed up processing, the computer stores
# up file writes in a buffer and only
# writes when it is full. The close command
# will write the last little piece in the buffer
# and should be tested for error.
close OUTFILE or die "cannot write to output: $!";
# Now move the new file to the old.
move( "$inputFile.tmp", $inputFile );
__END__
You mentioned that you want to add more records to the end but you
haven't indicated what they are.
--
Just my 0.00000002 million dollars worth,
--- Shawn
"Probability is now one. Any problems that are left are your own."
SS Heart of Gold, _The Hitchhiker's Guide to the Galaxy_
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