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Small Help on SED

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# 1  
Old 09-19-2006
Small Help on SED
Hi All,
I have come across a command

echo "123 abc" | sed 's/[0-9]*/& &/'

output is

123 123 abc

then i tried in different ways to get 123 abc abc as output.

Can u please explain me the importance of & in the above command.

Thank you
- Chanakya
# 2  
Old 09-19-2006
This is from the sed man page:
Code:
                  An ampersand (&) appearing in the  replacement
                  will  be  replaced  by the string matching the
                  RE.

This means that the sed will replace & with 123 (the string that matches the regular expression in this example). Since the & occurs twice, it is placed there twice.
# 3  
Old 09-19-2006
Thank you blowtorch ..
Expecting the same i tried

echo 123 abc | sed 's/*[a-z]/& &/' to get 123 abc abc as output but i could not ..can u guide me how to get the desired output
# 4  
Old 09-19-2006
try this:

Code:
echo 123 abc | sed 's/\([a-z].*\)/& &/'

# 5  
Old 09-19-2006
Try this :
Code:
echo "123 abc" | sed 's/[a-z]\{1,\}/& &/'

Another example of sed :
Code:
echo "++++ 123 abc ----" | sed 's/\([0-9]\{1,\}\)[[:space:]]*\([a-z]\{1,\}\)/Number=\1 Text=\2/'

Output:
++++ Number=123 Text=abc ----



Jean-Pierre.
# 6  
Old 09-19-2006
hi aigles,
thank you.. I got the required output. Can u explain me what is wrong in

echo 123 abc | sed 's/\([a-z].*\)/& &/' and if possible explain ur command also echo "123 abc" | sed 's/[a-z]\{1,\}/& &/'

-Chanakya
# 7  
Old 09-19-2006
The regex [a-z].* matches one alphabetic character and all following characters.
For example, the command :
Code:
echo 123 abc 456 | sed 's/\([a-z].*\)/& &/'

gives the ouput:
Code:
123 abc 456 abc 456

Code:
echo "123 abc" | sed 's/[a-z]\{1,\}/& &/'

The regex [a-z]\{1,\} matches one or more alphabtic character.
Some commands accept the following syntax [a-z]+

Jean-Pierre.
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