Sed search and replace on variable string

Question

I'm trying to search and replace a string in a file on the Mac Terminal using sed. I'm able to search and replace a simple string:

sed -i.bak 's/HOSTS/BOASTS/g' file.txt

But I'm trying it on something a little more complicated, basically the string I want to replace looks something like 'HOSTS:"123.123.123.123, 12345"' - with the 123.123.123.123 being a variable IP so I can't exactly search for that, so I'm trying to use regular expressions, mainly the "." to indicate that I don't know what the IP address will be.

I've tried the following with no luck:

sed -i.bak 's/HOSTS:"., 00000"/HOSTS:"999.999.999.999, 00000"/g' file.txt

Vinicius Placco · Accepted Answer · 2016-08-08 20:07:45Z

1

You could try the following:

echo "HOSTS:\"123.123.123.123, 12345\"" | sed -e 's/[0-9][0-9][0-9]\.[0-9][0-9][0-9]\.[0-9][0-9][0-9]\.[0-9][0-9][0-9]/999.999.999.999/g'.

each [0-9] will look for a digit, and each \. is the actual symbol, not the "match a character" symbol on sed. This assumes that the IPs will always have this structure. If you're dealing with xxx.xxx.xxx.xxx:xxxx you'll have to edit accordingly.

answered Aug 8, 2016 at 20:07

Vinicius Placco

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sage Over a year ago

I suggest a more permissive IP regex: [0-9]\+\.[0-9]\+\.[0-9]\+\.[0-9]\+/ where '\+' signals 1 or more of the preceding character This will work for IP addresses such as 4.2.2.2 (a valid IP).

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