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redircting output of one script as input to another

msds
User

Sep 22, 2002, 11:47 PM

Post #1 of 16 (1093 views)

redircting output of one script as input to another	Can't Post

Hello, I want to combine three perl scripts into one piece of functioning code.Suppose,

Quote

a)prog1.pl reads an input string,

/does some proccessing/

produces $string1 as output, which it writes to the file : firstfile.txt

b)prog2.pl then reads $string1 as input from firstfile.txt

/does some proccessing/

produces $string2 as output, which it writes to the file : secondfile.txt

c)prog3.pl reads $string2 as input from secondfile.txt

/does some proccessing/

produces $string3 as output, which it writes to thirdfile.txt

The thirdfile.txt has the final required output.

Is there a way in which we can have a kind of "main.pl "
program, in which prog1.pl,prog2.pl,and prog3.pl can be made to execute one after the other.i.e we run the main.pl program , and check for the results in thirdfile.txt

Any help would be appreciated.
Thanx,
msds Smile

davorg
Thaumaturge / Moderator

Sep 23, 2002, 6:02 AM

Post #2 of 16 (1081 views)

Re: [msds] redircting output of one script as input to another [In reply to]	Can't Post

Well, Perl programs are just programs. You can run another Perl program just the same way as you can any other external program. In this case it sounds like "system" will do what you want.

It may be worth considering changing your programs to modules. That would make them easier to reuse.

Dave...

--
Dave Cross, Perl Hacker, Trainer and Writer
http://www.dave.org.uk/
Get more help at Perl Monks

Strider
Novice

Sep 25, 2002, 11:32 AM

Post #3 of 16 (1076 views)

Re: [msds] redircting output of one script as input to another [In reply to]	Can't Post

Quote

I want to combine three perl scripts into one piece of functioning code.

From your description, you have three separate text files being created but only one contains the data of interest. As I read it you want to keep everything in one script and just use function calls to arrive at the final required data.

Is this conclusion wrong? Are you asking for help with function calls? Or are you looking to create a new script to control the existing ones? I'd like to help, but I am a little unclear on exactly how you intend the script to function.

David

msds
User

Sep 26, 2002, 10:21 PM

Post #4 of 16 (1068 views)

Re: [davorg] redircting output of one script as input to another [In reply to]	Can't Post

Thanx Dave. I'm trying to convert prog1.pl, prog2.pl, and prog3.pl into subroutines, then call them in sequence
inside main.pl.I'm trying it with some simple code before
putting actual code into prog1.pl, prog2.pl, and prog3.pl .

Also what are the possible related skills it is helpful for a Perl programmer to have?
Thanx, msds Smile

msds
User

Sep 26, 2002, 11:44 PM

Post #5 of 16 (1065 views)

Re: [Strider] redircting output of one script as input to another [In reply to]	Can't Post

Hello David,

Quote

As I read it you want to keep everything in one script and just use function calls to arrive at the final required data.

That's what I'm thinking of.

Here is the code I tried:
prog1.pl:

Code

 
sub first{ 
 
$result="firstoutput"; 
 
open OUTPUT,'>op.txt' or die $!; 
 
print OUTPUT $result; 
 
close OUTPUT; 
 
}

prog2.pl:

Code

 
sub second{ 
 
open OUTPUT,'op.txt' or die $!; 
 
while($result2=<OUTPUT>) 
{ 
   
open SUGGEST, '>inpsug.txt' or die $!; 
 
print SUGGEST "\nThe soundex code of the word is:"; 
 
print SUGGEST $result2; 
 
close OUTPUT; 
 
close SUGGEST; 
 
} 
}

prog3.pl:

Code

sub third { 
 
open SUGGEST, 'inpsug.txt' or die $!; 
 
while($finp=<SUGGEST>) 
{ 
  
 #print "\n$finp"; 
  
 open FOUPT, '>fiop.txt' or die $!; 
  
 print FOUPT $finp; 
  
 close FOUPT; 
  
 close SUGGEST; 
  
 } 
  
}

main.pl:

Code

require "prog1.pl"; 
require "prog1.pl"; 
require "prog1.pl"; 
 
do first(); 
do second(); 
do third();

On running main.pl, I get the following error message:

prog1.pl did not return a true value at C:\monisha\perlpractise\main.pl line 1.

Tool completed with exit code 255

What is the mistake I've made here? Crazy

Thanx,msds Smile

davorg
Thaumaturge / Moderator

Sep 27, 2002, 1:30 AM

Post #6 of 16 (1063 views)

Re: [msds] redircting output of one script as input to another [In reply to]	Can't Post

Any file loaded by "use" or "require" must return a true value to the calling program.

This is usually achieved by simply putting a line containing

Code

1;

at the end of the file.

--
Dave Cross, Perl Hacker, Trainer and Writer
http://www.dave.org.uk/
Get more help at Perl Monks

Strider
Novice

Sep 27, 2002, 5:52 AM

Post #7 of 16 (1060 views)

Re: [msds] redircting output of one script as input to another [In reply to]	Can't Post

Getting back to thought of combining everything into one script, you could do something similar to this:

Code

#!/usr/bin/perl  
 
############################################ 
# Restrict unsafe programming constructs 
#    - always good to include,  
#      even if not utilized at first 
############################################ 
use strict;  
 
############################################ 
# Method: first 
############################################ 
sub first() 
{ 
    return "firstoutput"; 
}  
 
############################################ 
# Method: second 
############################################ 
sub second() 
{ 
    return "\nThe soundex code of the word is:"; 
}  
 
############################################ 
# Method: third 
############################################ 
sub third() 
{ 
    return sprintf("%s %s", 
                   second(), 
                   first()); 
}  
 
############################################ 
# Main 
############################################ 
printf("%s\n", 
       third());

Of course, this is just a sample and could be simplified even more depending on how you intend to use it. The main point is that, unless needed, output to a file can be avoided by using return values on the sub procedures. I may be missing the question and stating the obvious, but hopefully this helps some.

David

msds
User

Sep 29, 2002, 9:59 PM

Post #8 of 16 (1053 views)

Re: [Strider] redircting output of one script as input to another [In reply to]	Can't Post

Thanks David,
got ur point.But actually, the string that
prog1.pl outputs(firstoutput), needs to be proccessed in
prog2.pl, which then outputs another string to prog3.pl.

prog3.pl further proccesses,and returns the reqd output string.
Hmm, but yes we can return values to subroutines instead of writing to files,even then.Then we'd have to pass one para from prog1.pl to prog2.pl, process in prog2.pl, pass the result as a para to prog3.pl.Yes , I'll try that.Thanx
msds Smile

msds
User

Sep 29, 2002, 10:08 PM

Post #9 of 16 (1052 views)

Re: [davorg] redircting output of one script as input to another [In reply to]	Can't Post

Thanx Dave,

The 1; took care of the error I was getting.main.pl executes without any errors, but I'm not getting the
required output in fiop.txt.

This part is O.K:

The file op.txt gets the following written onto it:

firstoutput

The file inpsug.txt gets the following written onto it:

The code of the word is:firstoutput

The file fiop.txt gets created, but nothing gets written onto it. I need the string "firstoutput" to get written
onto it.

What could be the problem here? Unsure

Thanx, msds Smile

Strider
Novice

Sep 30, 2002, 5:01 AM

Post #10 of 16 (1047 views)

Re: [msds] redircting output of one script as input to another [In reply to]	Can't Post

Post your code, or at least that portion where you are attempting to write to fiop.txt. I'll have a better chance of answering your question if I can see exactly what is being done.

David

msds
User

Sep 30, 2002, 10:01 PM

Post #11 of 16 (1040 views)

Re: [Strider] redircting output of one script as input to another [In reply to]	Can't Post

Hello David, the code which I'm trying to execute
, in which nothing gets written to fiop.txt, is already
present at the beginning of the thread .But here it is again anyway.:

Code

 
prog1.pl:  
 
sub first{   
  $result="firstoutput";   
  open OUTPUT,'>op.txt' or die $!;   
  print OUTPUT $result;   
  close OUTPUT; 
} 
 
1; 
 
prog2.pl:  
 
sub second { 
  open OUTPUT,'op.txt' or die $!; 
  while($result2=<OUTPUT>) { 
    open SUGGEST, '>inpsug.txt' or die $!; 
    print SUGGEST "\nThe soundex code of the word is:"; 
    print SUGGEST $result2; 
    close OUTPUT; 
    close SUGGEST; 
  } 
} 
 
1; 
 
prog3.pl:  
 
sub third { 
  open SUGGEST, 'inpsug.txt' or die $!; 
  while($finp=<SUGGEST>) { 
    #print "\n$finp"; 
    open FOUPT, '>fiop.txt' or die $!; 
    print FOUPT $finp; 
    close FOUPT; 
    close SUGGEST; 
  } 
} 
 
1; 
 
main.pl:  
 
require "prog1.pl"; 
require "prog1.pl"; 
require "prog1.pl"; 
 
do first(); 
do second(); 
do third();

Thanx, msds Smile

(This post was edited by davorg on Oct 1, 2002, 1:27 AM)

davorg
Thaumaturge / Moderator

Oct 1, 2002, 1:45 AM

Post #12 of 16 (1036 views)

Re: [msds] redircting output of one script as input to another [In reply to]	Can't Post

I suggest that you turn on "-w" and "use strict" in all of your Perl programming as they will help you find many problems in your code.

In this case, you have a couple of loops that look like this:

Code

open FILE, 'file' or die $!; 
while (<FILE>) { 
  # do something 
  close FILE; 
}

Take a second to think what this does.

You read the first line from the file and process the line in some way. You then close the filehandle. You then go back to the start of the loop and try to read the next line from the file. Except you can't because the filehandle is now closed. "-w" would give you a warning at this point telling you that you're trying to read from a closed filehandle.

Of course, in most cases this doesn't matter to you, as your files only have one line in them, but look at the code that writes data into inpsug.txt:

Code

print SUGGEST "\nThe soundex code of the word is:";  
print SUGGEST $result2;

You're writing _two_ lines of data into the file. The first of these is empty (it ends with the newline character). Therefore when you come to read this data later on (using one of your normal, broken loops) you only read the first, empty line - and it's that which ends up being written to fiop.txt.

_Please_ learn to program with "-w" and "use strict". It will make your life (and mine) much easier :)

--
Dave Cross, Perl Hacker, Trainer and Writer
http://www.dave.org.uk/
Get more help at Perl Monks

msds
User

Oct 1, 2002, 4:55 AM

Post #13 of 16 (1031 views)

Re: [davorg] redircting output of one script as input to another [In reply to]	Can't Post

ur the one Dave! Now the code works.
Sheesh.. Blush

I don't think I'm ever going
to forget about "strict" or "-w" now.
Thanx,
msds

msds
User

Oct 10, 2002, 4:52 AM

Post #14 of 16 (1019 views)

Re: [davorg] redircting output of one script as input to another [In reply to]	Can't Post

Hello Dave .

I tried some similar towhat we have been discussing:

Code

use strict; 
use warnings; 
 
require "x.pl"; 
require "y.pl"; 
require "z.pl"; 
 
do one(); 
do two(); 
do three();

I get the following error message:

Use of "do" to call subroutines is deprecated at C:\soandso\appli.pl line 8.

Use of "do" to call subroutines is deprecated at C:\soandso\appli.pl line 9.

Use of "do" to call subroutines is deprecated at C:\soandso\appli.pl line 10.

Can't locate y.pl in @INC (@INC contains: D:/Perl/lib D:/Perl/site/lib .) at C:\soandso\appli.pl line 5.

Tool completed with exit code 2

What is the problem here?
Thanx,
msds

davorg
Thaumaturge / Moderator

Oct 10, 2002, 5:13 AM

Post #15 of 16 (1018 views)

Re: [msds] redircting output of one script as input to another [In reply to]	Can't Post

Well, I think that Perl's error messages are generally very easy to understand. Certainly these ones mean exactly what they say.

If you ever have error messages that you don't understand, it's a good idea to add

Code

use diagnostics;

to your program. Then instead of getting one line error messages, you'll get a paragraph of useful information.

--
Dave Cross, Perl Hacker, Trainer and Writer
http://www.dave.org.uk/
Get more help at Perl Monks

msds
User

Oct 25, 2002, 3:47 AM

Post #16 of 16 (994 views)

Re: [davorg] redircting output of one script as input to another [In reply to]	Can't Post

Thanx Dave.
Made a silly mistake like typing the name of the second file included, i.e. soundgenr.pl incorrectly.@INC had soungenr.pl in it.

Sorry for being so late in replying!

Thanx,
msds Smile

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