Use script instead of regex for Nginx prox_redirect to modify Location header

Question

For Nginx, proxy_redirect, can we use a string instead of string or regex? I have a need to replace multiple occurrences of text in the Location string using proxy_redirect and I am not sure how to do it with regex. Therefore, I am checking if the proxy_redirect can make us of script, then it could be easy.

You can use several proxy_redirect statements in a block, but can you give an example of what you are trying to achieve? — Richard Smith
– Richard Smith, Commented Sep 1, 2020 at 6:11
Here is another question that describes overall problem I am trying to solve with proxy_redirect. stackoverflow.com/questions/63647067/… — Krunal
– Krunal, Commented Sep 1, 2020 at 6:12
With single occurrence of text to change in a string, regex works, but with multiple occurrences regex is not possible. And I think if it supports script then it can be done easily. — Krunal
– Krunal, Commented Sep 1, 2020 at 6:13
How many occurrences of the string are there likely to be? You could write a regex to handle one occurrence, and another to handle two occurrences, etc. — Richard Smith
– Richard Smith, Commented Sep 1, 2020 at 6:36
There are three occurrences as of now. Any hint or reference how to do this is great! — Krunal
– Krunal, Commented Sep 1, 2020 at 6:40

Richard Smith · Accepted Answer · 2020-09-01 09:28:55Z

1

You can use multiple proxy_redirect statements within a single block containing the proxy_pass statement. Nginx evaluates statements containing regular expressions in order until a match is found, so place the more specific regular expressions before the less specific ones.

To replace a single occurrence of a pattern within the Location header of a 3xx response, you would use:

proxy_redirect ~^(.*)origin.example.com(.*)$ $1main.example.com$2;

To replace two occurrences of the same pattern, you would use:

proxy_redirect ~^(.*)origin.example.com(.*)origin.example.com(.*)$ $1main.example.com$2main.example.com$3;

To replace one, two or three occurrences of the same pattern, you would use:

proxy_redirect ~^(.*)origin.example.com(.*)origin.example.com(.*)origin.example.com(.*)$ $1main.example.com$2main.example.com$3main.example.com$4;
proxy_redirect ~^(.*)origin.example.com(.*)origin.example.com(.*)$ $1main.example.com$2main.example.com$3;
proxy_redirect ~^(.*)origin.example.com(.*)$ $1main.example.com$2;

Use ~* to make the regular expression case-insensitive. See this document for details.

answered Sep 1, 2020 at 9:28

Richard Smith

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1 Comment

Krunal Over a year ago

wow, this works fine. I got an exact idea. Thanks for guiding.

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