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Adding Prefixes.

Ndx
Novice

Jul 28, 2009, 9:38 AM

Post #1 of 22 (8390 views)

Adding Prefixes.	Can't Post

Hello,

I'm trying to make a small script that will edit a text file.

1st - It will search and replace some text - I was able to get it working thx to this site and google.

2nd It will add prefix for each line. ( I'm not sure how to specify lines ie: 1 Line prefix will be "XB", Line 2 prefix "WW" etc.

Is there any easy way to do it ?

Before:

Code

Perl Noobie 
Perl Master 
Perl Who

After:

Code

WB Perl Noobie 
XX Perl Master 
TT Perl Who

I would appreciate some help or some sample code...

Thank You!

(This post was edited by Ndx on Jul 28, 2009, 9:39 AM)

FishMonger
Veteran / Moderator

Jul 28, 2009, 9:49 AM

Post #2 of 22 (8385 views)

Re: [Ndx] Adding Prefixes. [In reply to]	Can't Post

Create an array or a hash that maps the line number to the prefix, then use the line number to look up the prefix value in the array or hash.

Since you're needing sequential numbering for the indexing (i.e., the line numbers), an array would be the normal choice to hold the prefix data. But you need to remember that arrary's are 0 indexed, so you'll need to account for that when accessing the array element.

johnpc831
Novice

Jul 28, 2009, 9:50 AM

Post #3 of 22 (8384 views)

Re: [Ndx] Adding Prefixes. [In reply to]	Can't Post

The way I usually do stuff like this is to read in the whole file, make changes, and then write everything back to the file.

Code

open(FH,"myfile.txt"); 
my @lines = <FH>; 
close(FH); 
 
my $prefix = 'TT'; # Or whatever your prefix is supposed to be 
 
open(FH,">myfile.txt"); 
foreach(@lines){ 
    print FH "$prefix $_"; 
} 
close(FH);

Ndx
Novice

Jul 28, 2009, 10:00 AM

Post #4 of 22 (8382 views)

Re: [johnpc831] Adding Prefixes. [In reply to]	Can't Post

In Reply To

The way I usually do stuff like this is to read in the whole file, make changes, and then write everything back to the file.

Code

open(FH,"myfile.txt"); 
my @lines = <FH>; 
close(FH); 
 
my $prefix = 'TT'; # Or whatever your prefix is supposed to be 
 
open(FH,">myfile.txt"); 
foreach(@lines){ 
    print FH "$prefix $_"; 
} 
close(FH);

'
Thank You
This works great ... But it adds same prefix for all lines ..
I'm trying to have different prefix for each line ...

Code

#!/usr/bin/perl 
 
{  
  local $^I = "data2.bak";  # the backup extension  
  local @ARGV = "data.txt";  # the file to edit  
  while (<>) {  
    next if $. == 10;  # this will skip line 10  
    print "Test1!" if $. == 1;  # this in line 3  
    print;  # this prints the line itself  
    print "Test2!" if $. == 8;  # this in line 6  
  }  
}

I found this code in FAQ ..

Anyways :) Thank you very much guys :)

KevinR
Veteran

Jul 28, 2009, 10:35 AM

Post #5 of 22 (8379 views)

Re: [Ndx] Adding Prefixes. [In reply to]	Can't Post

Code

#!/usr/bin/perl  
  
{   
  local $^I = "data2.bak";  # the backup extension   
  local @ARGV = "data.txt";  # the file to edit   
  while (<>) {   
    next if $. == 10;  # this will skip line 10   
    print "Test1!" if $. == 1;  # this in line 3   
    print;  # this prints the line itself   
    print "Test2!" if $. == 8;  # this in line 6   
  }   
}

That is probably the way I would do it to having a preference for perls built-in editor over other possibilities. Maybe your example code was wrong, but you have:

print "Test1!" if $. == 1; # this in line 3
print "Test2!" if $. == 8; # this in line 6

clearly if $. == 1 then that is line one and same for $. == 8, that is line eight.
-------------------------------------------------

FishMonger
Veteran / Moderator

Jul 28, 2009, 10:54 AM

Post #6 of 22 (8376 views)

Re: [Ndx] Adding Prefixes. [In reply to]	Can't Post

If you're not adding a prefix to each line, then I'd use a hash and do this.

Code

#!/usr/bin/perl   
 
use strict; 
use warnings; 
 
my %prefix = ( 1 => 'Test1!', 
               8 => 'Test2!', 
} 
 
local $^I = "data2.bak";  # the backup extension    
local @ARGV = "data.txt";  # the file to edit    
while (<>) {    
    next if $. == 10;  # this will skip line 10    
 
    print $prefix{$.} if exits $prefix{$.}; 
 
    print;  # this prints the line itself 
}

KevinR
Veteran

Jul 28, 2009, 11:01 AM

Post #7 of 22 (8373 views)

Re: [FishMonger] Adding Prefixes. [In reply to]	Can't Post

In Reply To

If you're not adding a prefix to each line, then I'd use a hash and do this.

Code

#!/usr/bin/perl   
 
use strict; 
use warnings; 
 
my %prefix = ( 1 => 'Test1!', 
               8 => 'Test2!', 
} 
 
local $^I = "data2.bak";  # the backup extension    
local @ARGV = "data.txt";  # the file to edit    
while (<>) {    
    next if $. == 10;  # this will skip line 10    
 
    print $prefix{$.} if exits $prefix{$.}; 
 
    print;  # this prints the line itself 
}

The hash is a good suggestion but I think the code is not quite right:

This line:

Code

    print $prefix{$.} if exits $prefix{$.};

Should be:

Code

    print "$prefix{$.} $_" if exists $prefix{$.};

Fish, you had "exits" instead of "exists" which is obviously just a typo but I bring it to your attention.
-------------------------------------------------

Ndx
Novice

Jul 28, 2009, 11:17 AM

Post #8 of 22 (8371 views)

Re: [KevinR] Adding Prefixes. [In reply to]	Can't Post

Hi Thank You ...

When I'm trying to execute this I'm getting ...

admin$ perl x.pl
syntax error at x.pl line 10, near "local"
Execution of x.pl aborted due to compilation errors.

I can't see anything wrong there

Code

#!/usr/bin/perl    
  
use strict;  
use warnings;  
  
my %prefix = { 1 => 'Test1!',  
               8 => 'Test2!',  
}  
   
local $^I = "data2.txt";  # the backup extension   
  local @ARGV = "data.txt";  # the file to edit   
  while (<>) {       
    next if $. == 10;  # this will skip line 10     
  
    print "$prefix{$.} $_" if exists $prefix{$.};  
  
    print;  # this prints the line itself  
}

And this ... Prints to 1st line .. then stops ... Don't know why :(

Code

#!/usr/bin/perl  
  
{   
  local $^I = "data2.txt";  # the backup extension   
  local @ARGV = "data.txt";  # the file to edit   
  while (<>) {    
    print "Powered " if $. == 1;   
    print "Test " if $. == 2;   
    print "Energy " if $. == 3;   
    print "Voltage " if $. == 4;     
    print "Watts " if $. == 5;  
    print "Output " if $. == 6;   
    print "Nano " if $. == 7;     
    print "Particles " if $. == 8;  
    print "Uoa " if $. == 9;  
    print "Version " if $. == 10;    
    print "Test " if $. == 11;   
    print "EU " if $. == 12;   
    print "V2 " if $. == 13;   
    print "V3 " if $. == 14;   
    print "V1 " if $. == 15; 
    print;   
    
  }   
}

(This post was edited by Ndx on Jul 28, 2009, 11:20 AM)

KevinR
Veteran

Jul 28, 2009, 11:24 AM

Post #9 of 22 (8366 views)

Re: [Ndx] Adding Prefixes. [In reply to]	Can't Post

Looks like our friend Fish was posting too quickly, there is a mistake here:

Code

my %prefix = ( 1 => 'Test1!',   
               8 => 'Test2!',   
}

should be:

Code

my %prefix = ( 1 => 'Test1!',   
               8 => 'Test2!',   
);

Or maybe he didn't get his cup of java today Wink

-------------------------------------------------

FishMonger
Veteran / Moderator

Jul 28, 2009, 11:28 AM

Post #10 of 22 (8365 views)

Re: [Ndx] Adding Prefixes. [In reply to]	Can't Post

Oops,

Code

my %prefix = { 1 => 'Test1!',   
               8 => 'Test2!',   
}

Should have been

Code

my %prefix = { 1 => 'Test1!',   
               8 => 'Test2!',   
);

KevinR
Veteran

Jul 28, 2009, 11:28 AM

Post #11 of 22 (8365 views)

Re: [Ndx] Adding Prefixes. [In reply to]	Can't Post

Quote

And this ... Prints to 1st line .. then stops ... Don't know why :(

I don't see why it would stop at the first line. But that is clearly not a good way to go about your task. You are forcing the script to evaluate each "if" condition unnecessarily. Use the hash or use an if/elsif/elsif/...../else block.
-------------------------------------------------

KevinR
Veteran

Jul 28, 2009, 11:29 AM

Post #12 of 22 (8362 views)

Re: [FishMonger] Adding Prefixes. [In reply to]	Can't Post

In Reply To

Oops,

Code

my %prefix = { 1 => 'Test1!',   
               8 => 'Test2!',   
}

Should have been

Code

my %prefix = { 1 => 'Test1!',   
               8 => 'Test2!',   
);

Fish, its still wrong. Unsure

-------------------------------------------------

FishMonger
Veteran / Moderator

Jul 28, 2009, 11:30 AM

Post #13 of 22 (8361 views)

Re: [KevinR] Adding Prefixes. [In reply to]	Can't Post

I definitely would not use the if/elsif/elsif approach. That would get very messy.

Use an array or a hash.

KevinR
Veteran

Jul 28, 2009, 11:33 AM

Post #14 of 22 (8359 views)

Re: [FishMonger] Adding Prefixes. [In reply to]	Can't Post

In Reply To

I definitely would not use the if/elsif/elsif approach. That would get very messy.

Me either, but I sure wouldn't use if/if/if which is just inefficient since the condition can only ever be true once per line of the file. The hash looks to be the way to go.
-------------------------------------------------

FishMonger
Veteran / Moderator

Jul 28, 2009, 11:36 AM

Post #15 of 22 (8358 views)

Re: [KevinR] Adding Prefixes. [In reply to]	Can't Post

In Reply To

Fish, its still wrong. Unsure

I must be real tired, I copy/past the wrong one. Blush

Code

my %prefix = ( 1 => 'Test1!',    
               8 => 'Test2!',    
);

FishMonger
Veteran / Moderator

Jul 28, 2009, 11:38 AM

Post #16 of 22 (8357 views)

Re: [KevinR] Adding Prefixes. [In reply to]	Can't Post

Quote

The hash looks to be the way to go.

The has is IMO more readable, but the array would be the most efficient.

KevinR
Veteran

Jul 28, 2009, 11:42 AM

Post #17 of 22 (8353 views)

Re: [FishMonger] Adding Prefixes. [In reply to]	Can't Post

In Reply To

Quote

The hash looks to be the way to go.

The has is IMO more readable, but the array would be the most efficient.

Yea, after looking back at it, since there are all sequential it should be the best way.
-------------------------------------------------

Ndx
Novice

Jul 28, 2009, 11:42 AM

Post #18 of 22 (8350 views)

Re: [KevinR] Adding Prefixes. [In reply to]	Can't Post

Thank You Guys,

I'm crazzy or something is wrong ...

Code

#!/usr/bin/perl    
  
use strict;  
use warnings;  
  
my %prefix = ( 1 => 'Test2!',    
               2 => 'Test3!', 
	       3 => 'Test4!',    
               4 => 'Test5!',     
); 
  
local $^I = "data2.bak";  # the backup extension     
local @ARGV = "data.txt";  # the file to edit     
while (<>) {     
      
    print "$prefix{$.} $_" if exists $prefix{$.};  
}

Again it prints only in 1st line then stops.

data.txt
@� NanoVolt-Uno-Quad-Small: 324786 +345
@� NanoVolt-Uno-Quad-Small: 35436 +545
@� NanoVolt-Uno-Quad-Small: 8888.51 +145
@� NanoVolt-Uno-Quad-Small: 56445 +54
@� NanoVolt-Uno-Quad-Small: 56435 +1657

Whats funny ... If I create a file called a new data.txt Inside..

28347298 893729873
87236478 783624876
78236476 738264678
32874888 283976489

It prints perfectly fine to this file!

(This post was edited by Ndx on Jul 28, 2009, 11:46 AM)

Ndx
Novice

Jul 28, 2009, 12:00 PM

Post #19 of 22 (8340 views)

Re: [Ndx] Adding Prefixes. [In reply to]	Can't Post

O I know whats wrong ... Don't know how to fix it lol!

Original "data.txt"
When I open it with txt editor looks fine:
@� NanoVolt-Uno-Quad-Small: 324786 +345
@� NanoVolt-Uno-Quad-Small: 35436 +545
@� NanoVolt-Uno-Quad-Small: 8888.51 +145
@� NanoVolt-Uno-Quad-Small: 56445 +54

But when I open it with VI editor I'm getting:

@� NanoVolt-Uno-Quad-Small: 324786 +345^M@� NanoVolt-Uno-Quad-Small: 35436 +545^M@� NanoVolt-Uno-Quad-Small: 8888.51 +145^M@� NanoVolt-Uno-Quad-Small: 56445 +54^M

So it stops at 1st line because it looks like there is no more lines ...

what ^M stands for ? Is there a easy way to parase it .. ?

Ndx
Novice

Jul 28, 2009, 1:12 PM

Post #20 of 22 (8335 views)

Re: [Ndx] Adding Prefixes. [In reply to]	Can't Post

solution:

perl -pi -e 's|\r|\n|g' data.txt

KevinR
Veteran

Jul 28, 2009, 1:21 PM

Post #21 of 22 (8334 views)

Re: [Ndx] Adding Prefixes. [In reply to]	Can't Post

Files was created on a Mac? Windows would be \r\n and Mac should just be \r (or ^M). Unix is \n.
-------------------------------------------------

Ndx
Novice

Jul 28, 2009, 1:22 PM

Post #22 of 22 (8333 views)

Re: [KevinR] Adding Prefixes. [In reply to]	Can't Post

In Reply To

Files was created on a Mac? Windows would be \r\n and Mac should just be \r (or ^M). Unix is \n.

Mac, Thank You good to know

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