perl script for file processing


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# 1  
Java perl script for file processing

Aim:

To scan a file and ignore all characters that has an ASCII value from 0 to 31 and 127 to 255 and accept only those characters having an ASCII between 32 and 126.

Script:

#!/usr/local/bin/perl
$filename = "$ARGV[0]";
if (-e $filename)
{
open(OUT, "${filename}") || die "can't open $filename\n";
while (<OUT>){
$found= "";
$stat=0;
chomp $_;
my @charArray = split(//, $_);
my $ref = \@charArray;
foreach (@charArray) {
$val = ord($$ref[$stat]);
if(($val>31)&&($val<127)){
$found = "$found$$ref[$stat]";
}
$stat++;
}
$found = "$found\n";
print $found;
}
close(OUT);
}

Problem:
The code mentioned above runs for 20-25 mins for a 500 MB file. This is very slow.


Can someone let me know if this can be done in a more efficient way so as to reduce the file processing duration?
# 2  
try this,

Code:
#! /opt/third-party/bin/perl

open(FILE, "<", $ARGV[0]) || die ("unable to open <$!>\n");

while( read(FILE, $data, 1) == 1 ) {
  $ordVal = ord($data);
  print "$ordVal"  if( $ordVal >= 32 && $ordVal <= 126 );
}

close(FILE);

exit(0);

# 3  
Hi Madhan,

Corrected code:

#!/usr/local/bin/perl
open(FILE, "<", $ARGV[0]) || die ("unable to open <$!>\n");
while( read(FILE, $data, 1) == 1 ) {
if((ord($data)>=32)&&(ord($data)<=126)){
print "$data";
}
if(ord($data)==10){
print "\n";}
}
close(FILE);

Its great it takes just 10 mins now. Is there anything else that can be done to reduce the duration further?
# 4  
Minor change but this will make a difference

change the following

Quote:
if((ord($data)>=32)&&(ord($data)<=126)){
print "$data";
}
if(ord($data)==10){
print "\n";}
}
to

Code:
print "$data" if((ord($data)>=32)&&(ord($data)<=126));

print "\n" if(ord($data)==10);

# 5  
Hi Madhan,

Thanks..It still takes 10 mins. I have one question here, if we are reading the entire file and moving one character by character won't it consume valuable memory? For eg in C we can take certain bytes (as first batch) from the file and process it and then follow with the next batch of the file.
Can anything be done here?

Please correct me if I am wrong.
# 6  
Quote:
It still takes 10 mins.
Are you testing with the same input file ?
And probably with the same load each time ?
# 7  
Quote:
For eg in C we can take certain bytes (as first batch) from the file and process it and then follow with the next batch of the file
Yes.

Probably you could try something like
Code:
while( read(FILE, $data, 1000) == 1000 ) {

and then split $data and use to process,
I think it will definitely reduce I/O here.

Let me know how it goes ! Smilie
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