CODEWITHSUNDEEP
linuxbashsedcommand-lineubuntu-18.04
Rolfen
Rolfen

Reputation: 47

how to replace substring in file without newlines in bash?

I have a config file template which I intend to use in the creation of a bash script to automate a installation task, the file has something like this (config.conf):

...
bootstrap_servers => "HUB_NAMESPACE.servicebus.windows.net:9093"
...

Also I get variables from another file which has something like this (vars.conf):

...
HUB_NAMESPACE:aNamespace
...

I want to replace HUB_NAMESPACE in config.conf. If I make the replacement using the following (there are several HUB_NAMESPACE to be replaced in the file):

HUB_NAMESPACE=$(awk -F: '/^.*HUB_NAMESPACE/{gsub(/ /,"",$2);print $2}' vars.conf)
sed -i 's^HUB_NAMESPACE^$HUB_NAMESPACE^g' config.conf

The resulting file will be something like this:

...
bootstrap_servers => "aNamespace
.servicebus.windows.net:9093"
...

Which causes the app to crash due to the newline between aNamespace and .servicebus.windows.net:9093".

Is there a way of preventing the insertion of the newline after replacing this way? Is there a better or simpler solution to replace substrings in a file?

Used commands extracted from here:

How get value from text file in linux

How to use sed to find and replace text in files

Also tried:

Remove newline from unix variable

Using sed's append/change/insert without a newline

Upvotes: 0

Views: 264

Answers (1)

user12859859
user12859859

Reputation:

I tested your command and it worked perfectly without any newline but in sed replace single quotes with double quotes.

HUB_NAMESPACE="$(awk -F: '/^.*HUB_NAMESPACE/{gsub(/ /,"",$2);print $2}' vars.conf)"

sed -i "s^HUB_NAMESPACE^$HUB_NAMESPACE^g" config.conf

Still if you are having problem then try below solution: A simple one liner that uses sed and awk without explicitely defining variable and with in-place file editing

sed -i "s/HUB_NAMESPACE/"$(awk -F: '/^.*HUB_NAMESPACE/{gsub(/ /,"",$2);printf "%s", $2}' vars.conf)"/g" config.conf

Output:

cat config.conf    
...
 bootstrap_servers => "aNamespace.servicebus.windows.net:9093" 
...

The newline insertion is prevented by using printf instead of print

Upvotes: 1

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