sed: problem while replacing string using wildcard

Question

I am trying to replace a string using the following command:

sed -e "s/\<$5\>/$6/g" "$2/$1" > "$4/$3"

$5-> "hostname=*"
$6-> "hostname=int1"
$2/$1-> "source file path"
$4/$3-> "destination file path" 

When I try to replace the following:

hostname=abc

I get,

hostname=int1=abc

But I want,

hostname=int1

How can I match string to achieve this?

Solution 1

sed uses regular expressions. These are different from patterns ("globs") that the shell uses.

Notice that the following doesn't work:

$ echo hostname=abc | sed "s/\<hostname=*\>/hostname=int1/"
hostname=int1=abc

But, the following does:

$ echo hostname=abc | sed "s/\<hostname=.*\>/hostname=int1/"
hostname=int1

You need a . before the *.

As a regular expression, hostname=* means hostname followed by zero or more equal signs. Thus sed "s/\<hostname=*\>/hostname=int1/" replaces hostname with hostname=int1.

By contrast, the regular expression hostname=.* means hostname= followed by zero or more any character at all. That is why s/\<hostname=.*\>/hostname=int1/ replaces hostname=abc with hostname=int1.

Solution 2

There might be a better solution than this but you can use the below command.

sed /hostname.*$/s//"hostname=int1"/g /home/path/of/your/original/file > /tmp/hello.$$

cat /tmp/hello.$$ > /home/path/of/your/original/file

Comments

[Atul Vekariya]

Please provide part of the source file you want to manage

[Sobrique]

This looks suspiciously like XML source. Is it?

[Menon]

Yes, this is part of the same script but not related to my question.