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Old 12-20-2006, 10:08 PM   #1
kscott121
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howto insert a string


I have a several thousand word document (in OpenOffice but it can be in a text document for processing) into which I would like to insert a known fixed string every X characters.

For instance suppose I wanted to insert the string "ABC" into the following after every 20 characters:

Twas the night before Christmas, when all through the house
not a creature was stirring, not even a mouse.

It would look something like:

Twas the night beforABCe Christmas, when alABCl through the house
ABCnot a creature was sABCtirring, not even a ABCmouse.

I tried to figure out a way to this seemingly straight forward action with sed and awk and even in Openoffice. The use of regular expressions seems promising but I couldn't solve it. Also problematic was the need to use multiple lines vs just each line alone.

If anyone can get me on the right track or recommend another tool, I'd appreciate it.
Thanks and Merry Christmas!!
Ken
I tried
sed 's/\(.*\)/ABC\1/' foo2.txt
and it puts ABC at the beginning of each line
 
Old 12-21-2006, 12:35 AM   #2
bigrigdriver
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You might be able to make it work as a shell script which takes a filename as input. Pseudo-code might look like this:

while not EOF
do
start counting characters and spaces
if character count == 20
then sed insert ABC
else
continue
fi
done

Now all you have to do is convert to the correct code.
 
Old 12-21-2006, 07:43 AM   #3
doc.nice
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in word macro language you could write a macro
(pseudocode!
Code:
cursor.pos = BOT
while not(cursor.pos == EOT) do
  cursor.left(20)
  document.insert("ABC")
done
HTH,
Flo
 
Old 12-24-2006, 09:55 AM   #4
archtoad6
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Is this what you're looking for?:
Code:
sed -r 's,(.{20}),\1ABC,g'
Code:
$ echo 'Twas the night before Christmas, when all through the house
 not a creature was stirring, not even a mouse.'  | sed -r 's,(.{20}),\1ABC,g'
Twas the night beforABCe Christmas, when alABCl through the house
 not a creature was ABCstirring, not even aABC mouse.
Notice, I did NOT use a text file initially; so I put the 2 lines of verse into "foo.txt", & tried:
Code:
cat foo.txt |sed -r 's,(.{20}),\1ABC,g'
as well as:
Code:
sed -r 's,(.{20}),\1ABC,g' foo.txt
Both worked:
Code:
$ cat foo.txt |sed -r 's,(.{20}),\1ABC,g'
Twas the night beforABCe Christmas, when alABCl through the house ABC
not a creature was sABCtirring, not even a ABCmouse.
Code:
$ sed -r 's,(.{20}),\1ABC,g' foo.txt
Twas the night beforABCe Christmas, when alABCl through the house ABC
not a creature was sABCtirring, not even a ABCmouse.
Before you ask "why?" or "how?", please read man sed especially the references in "See Also", especially the one to "regex(7)". If you have any Q's after that, please ask. If you're really interested in mastering sed & regex's, try explaining here what is going on.

Hint: There are 3 1/2, perhaps 4 1/2, "tricks", one of which you have already shown that you know.
 
Old 12-24-2006, 10:10 AM   #5
archtoad6
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Follow up & "Extra credit"

"Extra credit":
The feature of sed you are already using has a simpler alternative in this case, see if you can find it.


If you're not interested in playing this learning "game", I have the/my answers ready to post.

color test == LightBlue
 
Old 12-24-2006, 11:22 AM   #6
makyo
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Hi.
Quote:
Originally Posted by kscott121
...
Twas the night before Christmas, when all through the house
not a creature was stirring, not even a mouse.

It would look something like:

Twas the night beforABCe Christmas, when alABCl through the house
ABCnot a creature was sABCtirring, not even a ABCmouse.
Here is a perl hack that you should be able to modify to suit your needs. This is based on your input data, which I placed on file "data1":
Code:
#!/usr/bin/perl

# @(#) p1       Demonstrate text insertion with slurp.

use warnings;
use strict;

my($insert_distance) = 20;
my($out);
my($string) = "ABC";
my $text = do { local $/; <> }; # Perl Best Practices, p213
my($length) = length $text;

for( my $i = 0 ; $i < $length ; $i += $insert_distance ) {
        $out .= substr($text, $i, $insert_distance);
        $out .= $string;
}

print $out;

exit(0);
Which produces, when run:
Code:
% ./p1 data1
Twas the night beforABCe Christmas, when alABCl through the house
ABCnot a creature was sABCtirring, not even a ABCmouse
matching your desired output.

Best wishes for the season and the new year ... cheers, makyo
 
Old 12-26-2006, 03:50 PM   #7
archtoad6
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Oops!

A lesson in test files that are too short:

When applied to the whole poem (as d/l'd to foo2.txt), it is obvious that my code, too, starts over at the beginning of each line.

However, the following does work, I tested on the whole thing:
Code:
sed -r 'N;s,(.{20}),\1ABC,g' foo2.txt
Code:
$ sed -r 'N;s,.{20},&ABC,g' foo2.txt  | head
'Twas the night befoABCre Christmas, when aABCll through the houseABC
 not a creature waABCs stirring, not evenABC a mouse.
 The stockings were ABChung by the chimney ABCwith care,
 in hopeABCs that St. Nicholas ABCsoon would be there.ABC

The children were ABCnestled all snug in ABCtheir beds,
 while visions of suABCgar plums danced in ABCtheir heads.
 And MABCama in her 'kerchiefABC, and I in my cap,
 had just settled ouABCr brains for a long ABCwinter's nap.
How it works
  • -r keeps you from having to escape metacharacters.
  • N solves the "start over" problem by appending the next line.
  • , instead of '/' -- legibility: the 1st character after the 's' is the delimiter; any character is eligible, not just '/'.
  • {20} '{' & '}' make a bound that applies to the '.' wildcard.
  • & inserts the entire matched regex -- a little neater than "(...),\1".
  • g "rinse & repeat" through the whole line.

Hope this a) helps, & b) isn't too much showing off.


Comment
With all resect to Perl, Python, Ruby, & those who write them well; it's good to know the simple CLI tools also: tr, grep, sed, awk, etc.

Here we see a simple 1-liner that worked on the 2nd try, with no need to create a script file. Don't use an 8 pound sledge when a 16 ounce hammer will do. The higher level scripting languages are invaluable at the right time, but they are not the only answer.
<rant />
 
  


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