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problem with sed while replacing a string with another

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# 1  
Old 05-22-2009
problem with sed while replacing a string with another
Hi,
I have a line something like this

sys,systematic,system
I want to replace only the word system with HI

I used sed for this as below
echo sys,systematic,system | sed 's/system/HI/'

but I got output as
sys,HIatic,system

I wanted output as
sys,systematic,HI

Please tell me how can I achieve desired output?

Thanks
friendyboy
# 2  
Old 05-22-2009
If file is consistent, this might work

Code:
sed 's/system/HI/2' file

# 3  
Old 05-22-2009
Code:
sed -e 's/^system,/HI,/g' -e 's/,system$/,HI/g' -e 's/^system$/HI/g' -e 's/,system,/,HI,/g'  file.txt

irrespective of "system" position the above code will work.
# 4  
Old 05-22-2009
Thanks panyam
Thanks panyam,
I was looking for similar one irrespective of the position of word "system"
I have lots of lines with such set of words.Is there any shorter way of acheiving ?

Please suggest if any

Thanks
friendyboy
# 5  
Old 05-22-2009
sed's expression set is limited. You can achieve better results with perl:

Code:
perl -p -e 's/\bsystem\b/HI/g'

The \b encoding before and after essentially tells perl to look at "word boundaries". You can achieve a similar effect in sed with [^a-zA-Z0-9-_] but you still have to take care of beginning and end-of-line situations. Perl's \b does this automatically.
# 6  
Old 05-22-2009
The perl example is a good one.

If you must do it in sed, this one is a few characters shorter than the previous example Smilie

Code:
echo sys,systematic,system | sed -e 's/^/,/' -e 's/$/,/' -e 's/,system,/,HI,/g' -e 's/^,//' -e 's/,$//'

You could also do it in awk:

Code:
echo sys,systematic,system | awk 'BEGIN {FS=OFS=","} {for (i=1;i<=NF;i++) if ($i=="system") $i="HI"; print}'

# 7  
Old 05-22-2009
Thanks canbridge.
Infact I cant use perl inside the script.

If I want the output as
sys,systematic,bigredhat\HI

where bigredhat is the system name obtained by uname -n.

what modifications need to be done in ur awk example?

Thanks
friendyboy
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