Mastering Nginx

Appendix B

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As an example, we want to set a short text as the output for a file not found error in

a particular location. We specify the location with an equals sign (=) to exactly match
just this URI:

location = /image404.html {

return 404 "image not found\n";

}

Any call to this URI would then be answered with an HTTP code of 404, and the
text image not found\n. So, we can use /image404.html at the end of a try_files

directive or as an error page for image files.

In addition to directives relating to the act of rewriting a URI, the rewrite module

also includes the set directive to create new variables and set their values. This is
useful in a number of ways, from creating flags when certain conditions are present,

to passing named arguments on to other locations and logging what was done.

The following example demonstrates some of these concepts and the usage of the

corresponding directives:

http {

# a special log format referencing variables we'll define later

log_format imagelog '[$time_local] ' $image_file ' ' $image_type '

' $body_bytes_sent ' ' $status;

# we want to enable rewrite-rule debugging to see if our rule does

# what we intend

rewrite_log on;

server {

root /home/www;

location / {

# we specify which logfile should receive the rewrite-rule

debug

# messages

error_log logs/rewrite.log notice;

# our rewrite rule, utilizing captures and positional

variables