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Perl - CAPTURE query

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# 1  
Old 04-30-2010
Question Perl - CAPTURE query
When i run script with option 1 it works, however if I assign path to variable $tmpfile and try to use that it writes to $tmpfile and not /var/tmp/abc.tmp, what am I missing?

1.
open (CAPTURE, '>>tmpfile');
print CAPTURE "$T1,$T2,$T3";
close (CAPTURE);

2.
my $tmpfile='/var/tmp/abc.tmp';
open (CAPTURE, '>>$file');
print CAPTURE "$T1,$T2,$T3";
close (CAPTURE);
# 2  
Old 04-30-2010
What do you mean "with option 1 and 2" ?
Assuming that are two different scripts, than I guess the open line of the second script need to be adjusted to:
Code:
open (CAPTURE, '>>$tmpfile');

# 3  
Old 04-30-2010
Quote:
Originally Posted by gefa
When i run script with option 1 it works, however if I assign path to variable $tmpfile and try to use that it writes to $tmpfile and not /var/tmp/abc.tmp, what am I missing?

1.
open (CAPTURE, '>>tmpfile');
print CAPTURE "$T1,$T2,$T3";
close (CAPTURE);

2.
my $tmpfile='/var/tmp/abc.tmp';
open (CAPTURE, '>>$file');
print CAPTURE "$T1,$T2,$T3";
close (CAPTURE);
Change the single quotes ' ' in option 2 to double quotes " "

In Perl, no variable interpolation takes place inside single quotes but does in double quotes. In single quotes, open is trying to open a file literally called '$file" and of course fails.

You will solve your own problem on something like this if you check the return of open like so:

Code:
open (CAPTURE, ">>$file") || die "can't open $file cause $!"

Also, the for of open you are using there is being deprecated for a three argement form with a scalar handle. It allows the Perl interpreter to give you more meaningful error and compile errors if you use the 3 arg form of open:

Read about it here
# 4  
Old 05-04-2010
Many thanks for that.

Just another question how is possible to split a field within perl

for example in a file I might have something like these fields seperated by a space;

this is a test
again this is a test
...

I want to read the file line by line and split each line so that I have a variable containing field one and a second variable containing all other fields?

I can do this in awk but being new to perl I'm not sure how to do it in perl.
# 5  
Old 05-04-2010
The Perl operator split will split fields on whitespace or any other regular expression in one go.

Here is the documentation for that. (Or $ perldoc -f split at the command prompt) The part you want specifically is:

Code:
If EXPR is omitted, splits the $_ string.  If PATTERN is also
omitted, splits on whitespace (after skipping any leading
whitespace).

Here are some Perl resources:

Books:
Learning Perl

Programming Perl AKA The Camel Book

There are also tremendous resources on the web:

Each and every Perl tutorial These are also part of your Perl install in most cases. Type $ perldoc perlreftut at the command prompt for example.

Perlmonks and Perlmonks Tutorials

Perl Circus

Perl.com

IBM Perl One Liners

Perl 1 liners

Jaffe's regex tutorial

tye's ref reference

And once you know a bit of Perl, read the Perldoc site front to back
Last edited by drewk; 05-04-2010 at 11:17 AM..
# 6  
Old 05-05-2010
Thanks for the info, is it possible do do something like the following awk statement in perl as a one liner?
to split and populate the variable $acmodel with contents of field 19 which has more than word, the file $acfilename is seperated by comma however field 19 I'd like to put a comma after the the first word to effectively make two fields out of it.

e.g this is a test would become this, is a test

Code:
my $acmodel=`cat $acfilename |awk -F, '{print $19}' |awk '{ for (i=2 ; i<=NF ; i++) print $1,$i}'

Last edited by Scott; 05-05-2010 at 05:25 AM.. Reason: Code tags
# 7  
Old 05-05-2010
Quote:
Originally Posted by gefa
... is it possible do do something like the following awk statement in perl as a one liner?
to split and populate the variable $acmodel with contents of field 19 which has more than word, the file $acfilename is seperated by comma however field 19 I'd like to put a comma after the the first word to effectively make two fields out of it.

e.g this is a test would become this, is a test

Code:
my $acmodel=`cat $acfilename |awk -F, '{print $19}' |awk '{ for (i=2 ; i<=NF ; i++) print $1,$i}'

I am not sure if your awk script works the way you say it does.

Code:
$
$ ## the awk script, for the 4th field instead of the 19th
$ echo "abc,def,456,the good bad ugly,xyz" |awk -F, '{print $4}' |awk '{ for (i=2 ; i<=NF ; i++) print $1,$i}'
the good
the bad
the ugly
$
$

You may want to show us what the line in the file pointed at by the variable $acfilename looks like.

In any case, a Perl equivalent is as follows:

Code:
$
$ ## the Perl script
$ echo "abc,def,456,the good bad ugly,xyz" | perl -F, -lane '@x=split/ /,$F[3]; for($i=1; $i<=$#x; $i++){print "$x[0] $x[$i]"}'
the good
the bad
the ugly
$
$

tyler_durden

---------- Post updated at 09:35 AM ---------- Previous update was at 09:15 AM ----------
Quote:
Originally Posted by gefa
...
e.g this is a test would become this, is a test
...
On the other hand, if the 19th field in the comma-delimited file is:

Code:
this is a test

and you want to convert that to -

Code:
this, is a test

then here's an idea:

Code:
$
$
$ echo "1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,this is a test,20" | perl -pe 's/(([^,]*,){18}\w+)/$1,/'
1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,this, is a test,20
$
$

tyler_durden
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