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Number substitution with sed

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# 1  
Old 09-05-2012
Number substitution with sed
Hello,

Here is what i'm trying to do :
I want to replace any occurence of the string "abc=123" by "abc=999" except if the pattern is followed by a digit (I want to replace only "abc=123" and not "abc=1234")

One of the most promissing command I tried was :
Code:
 
echo 'abc=123
abc=1234
xyzabc=123&fghij=555&abc=123
abc=234'|sed 's/abc=123[^0-9]/abc=999/g'

but the output is :
Code:
abc=123
abc=1234
xyzabc=999fghij=555&abc=123
abc=234

What I'm trying to get is :
Code:
abc=999
abc=1234
xyzabc=999&fghij=555&abc=999
abc=234

Can anyone help ?
Last edited by nikop51000; 09-05-2012 at 12:23 PM.. Reason: forgot the & after 999 in the "What I'm trying to get" part
# 2  
Old 09-05-2012
Code:
$ echo 'abc=123
abc=1234
xyzabc=123&fghij=555&abc=123 abc=234' | sed 's/\b123\b/999/g'
Output:
abc=999
abc=1234
xyzabc=999&fghij=555&abc=999 abc=234

# 3  
Old 09-05-2012
You're matching the non-digit as part of the sed expression, but not including it in the replacement (hence your lost '&'). Try something like:
Code:
sed 's/abc=123\([^0-9]\)/abc=999\1/g'

(\1 is whatever matched the first bracket expression \(...\))
This User Gave Thanks to CarloM For This Post:
nikop51000
# 4  
Old 09-05-2012
This isn't maybe the best way, but it does work:


Code:
sed -E 's/$/./; s/abc=123([^0-9])/abc=999\1/g; s/.$//;'

At least with your small example.


If you are using AT&T's AST sed, or a BSD flavour of sed the -E option will be different.

---------- Post updated at 11:53 ---------- Previous update was at 11:49 ----------

@CarloM -- my thought exactly, but it still wasn't treating the newline as [^0-9], so I added the dot to ensure abc=123$ had some character after it. Maybe I was doing something wrong, but I couldn't get it to work just with the back reference.


Did I miss something?
This User Gave Thanks to agama For This Post:
CarloM
# 5  
Old 09-05-2012
sed -E uses ERE, so it should know alternation:
Code:
sed -E 's/abc=123([^0-9]|$)/abc=999\1/g'

These 3 Users Gave Thanks to Scrutinizer For This Post:
agama CarloM nikop51000
# 6  
Old 09-05-2012
Quote:
Originally Posted by agama
Did I miss something?
More likely I didn't notice, but I can't check right now.
# 7  
Old 09-06-2012
Thanks to all
Hi guys !
Thanks for all your messages !
I didn't think it would be so quick!

The -E option doesn't work with my sed (I'm on SunOS 5.10) so I'm now using this :
Code:
echo 'abc=123
abc=1234
xyzabc=123&fghij=555&abc=123abc=234' | sed -e 's/abc=123$/abc=999/g' -e 's/abc=123\([^0-9]\)/abc=999\1/g'

This is ok for me but I'd like to know if there's a better way...
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