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Add an string at every x chars

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# 1  
Old 12-05-2014
Add an string at every x chars
Hi All,

I have a file fo around 15k bytes which i need to insert a string
Code:
" + "

at every 250 bytes.

I found some ideas here using perl to split into lines and tried to addapt it but the results where not satisfactory


for instance i tried to change
Code:
#!/usr/bin/perl
$teststring = "1234567890abcdefghij0987654321ABCDEFGHIJlmnop";
@chunks = split /(.{10})/, $teststring;
foreach (@chunks) {
  printf "%s\n", $_;
}

into
Code:
  printf "%s\"  \+ \"", $_;

but somewho it ended up outputing the string i want to add twice and also it removed some of the code, where I have
Code:
\"

it removed the slash and left as
Code:
"

Any help appreciated.
# 2  
Old 12-05-2014
Hi kadu...

I have a file fo around 15k bytes which i need to insert a string

How are you expecting a file of size, say for example, 15173 bytes is size which is not exactly divisible by 250 to be handled?

With or without a final " + " ?

Do you want the above to be at the very start also?

Is the file going to contain any control characters or special characters or is it a pure alpha-numeric flat file?

An example real world file would help...

EDIT:
A simple longhand version using the shell only on OSX 10.7.5 default bash terminal every 7th character...
Code:
#!/bin/sh
# REMEMBER!!! A newline and/or carriage return are bytes also...
> /tmp/test_string
> /tmp/new_test_string
echo '1234567890abcdefghij0987654321ABCDEFGHIJlmnop
1234567890abcdefghij0987654321ABCDEFGHIJlmnop
1234567890abcdefghij0987654321ABCDEFGHIJlmnop
1234567890abcdefghij0987654321ABCDEFGHIJlmnop' > /tmp/test_string
count=0
text=$(cat /tmp/test_string)
echo "$text"
echo ""
while [ $count -lt ${#text} ]
do
	printf "${text:$count:7}" >> /tmp/new_test_string
	count=$((count+7))
	printf '" x "' >> /tmp/new_test_string
done
cat /tmp/new_test_string
echo ""

Results:-
Code:
Last login: Fri Dec  5 23:51:43 on ttys000
AMIGA:barrywalker~> cd Desktop
AMIGA:barrywalker~/Desktop> cd Code
AMIGA:barrywalker~/Desktop/Code> cd Shell
AMIGA:barrywalker~/Desktop/Code/Shell> ./addtext.sh
1234567890abcdefghij0987654321ABCDEFGHIJlmnop
1234567890abcdefghij0987654321ABCDEFGHIJlmnop
1234567890abcdefghij0987654321ABCDEFGHIJlmnop
1234567890abcdefghij0987654321ABCDEFGHIJlmnop

1234567" x "890abcd" x "efghij0" x "9876543" x "21ABCDE" x "FGHIJlm" x "nop
123" x "4567890" x "abcdefg" x "hij0987" x "654321A" x "BCDEFGH" x "IJlmnop" x "
123456" x "7890abc" x "defghij" x "0987654" x "321ABCD" x "EFGHIJl" x "mnop
12" x "3456789" x "0abcdef" x "ghij098" x "7654321" x "ABCDEFG" x "HIJlmno" x "p" x "
AMIGA:barrywalker~/Desktop/Code/Shell> _

Note the newlines are counted too.
Last edited by wisecracker; 12-05-2014 at 08:22 PM.. Reason: See above...
# 3  
Old 12-05-2014
Instead of the split you could try:
Code:
@chunks = ($teststring =~ /.{1,10}/g);

and then
Code:
printf "%s\" \+ \"\n", $_;

But then it will not work correctly for the last odd bit if string which is less than 10 characters. Also you mention bytes, which is not the same since the file may contain multibyte characters.

Also you seem to be introducing newlines in the which you did not mention in your requirement.
# 4  
Old 12-05-2014
Code:
sed 's/.\{250\}/&" + "/g' file

Quote:
Disclaimer: I'm aware of potential side effects.
# 5  
Old 12-05-2014
Quote:
Originally Posted by junior-helper
Code:
sed 's/.\{250\}/&" + "/g' file

Quote:
Disclaimer: I'm aware of potential side effects.
And, are you also aware that it only works if the entire file is a single line?

And, that since the standards only require sed to work on text files that on many systems are limited to lines no longer than 2048 bytes (including the <newline> characters), it might not work with a file that is around 15kb?
# 6  
Old 12-05-2014
  1. It depends on how one is interpreting this requirement. (I could be wrong.) In general, it will "work" on multiple lines too. (I understand what you are pointing to.)
  2. I'm aware of that (Actually, I've learned that from your previous postings, to be exact), but fortunately GNU sed has no such limit ¹
¹ https://www.gnu.org/software/sed/manual/sed.txt (Section: GNU `sed''s Limitations and Non-limitations)
# 7  
Old 12-06-2014
@junior-helper @2. Then you should explicitly mention with your solution that it needs GNU sed..
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