Question

I have to extract a parameter from a configuration file, and replace its values with another given value.
The config file is:

<host ip="200.200.200.200" name="testhost" description="test server" type="TEST_Duplex " connection="xmlrpc" xmldefaulttimeout="2.0" xmlspecifictimeout ="8.0"/>

I have to replace the value of xmldefaulttimeout="2.0" with another value, for example: xmldefaulttimeout="4.0".

As in the text, xmldefaulttimeout=”2.0″, but in fact, the value “2.0” is not certain. It may be another uncertain value. So I have to grep the value of xmldefaulttimeout and replace it with another given value (for example:4.0).

I think I have to use sed or awk. But I’m sorry my tried commands can’t realize this.
Could anybody help me with this? Thanks!
I’m sorry I just begin to learn shell:-)

Answer 1

input='<host ip="200.200.200.200" name="testhost" description="test server" type="TEST_Duplex " connection="xmlrpc" xmldefaulttimeout="2.0" xmlspecifictimeout ="8.0"/'

new_value='xmldefaulttimeout="4.0"'

echo $input | sed "s/xmldefaulttimeout=\"[0-9.]*\"/$new_value/"

To match any value for xmldefaulttimeout you’ll have to use a regex: xmldefaulttimeout=\"[0-9.]*\"

• xmldefaulttimeout= : Matched
  literally
• \" : To match a literal ", you need
  to escape the " to prevent
  premature ending of the pattern.
• [0-9.] : Char class to match any
  digit or a period
• * : zero or more of the previous char.