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selective removal of blank spaces in string

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# 1  
Old 10-07-2009
selective removal of blank spaces in string


I'm a newbie to shell scripting and I have the following problem:

I need all spaces between two letters or a letter and a number exchanged for an underscore, but all spaces between a letter and other characters need to remain. Searching forums didn't help...

One example for clarity:


force -- lamin 90 [label]
active A -- generation [label]

needed Output:

force -- lamin_90 [label]
active_A -- generation [label]

I tried solving this with sed but obviously s/ /_/g does not work, nor does any s/[a-zA-z0-9] [a-zA-z0-9]/[a-zA-z0-9]_[a-zA-z0-9]/g , because you just can't do this...

Can anyone help me?
Thanks in advance!
# 2  
Old 10-07-2009
echo 'force -- lamin 90 [label]' | sed 's/\([A-Za-z]\) \([0-9A-Za-z]\)/\1_\2/g'

# 3  
Old 10-07-2009
sed "s/\([A-Za-z]\) \+\([A-Za-z0-9]\)/\1_\2/g"

# 4  
Old 10-07-2009
Thanks a lot for the quick reply and the solution!!!

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