WEBVTT 00:04.300 --> 00:10.620 Now that we have an understanding of engine X variables we can move on to rewrites or simply redirect. 00:10.630 --> 00:17.320 In some cases the two directives we can use for rewriting requests is the rewrite directive and the 00:17.320 --> 00:23.060 return directive which we've already used several times throughout this course and being the same bluff. 00:23.080 --> 00:30.220 The two very importantly however the return statement as we've been using it takes a status code and 00:30.220 --> 00:33.040 response data or strings. 00:33.040 --> 00:40.630 But in the case of that response code being a 300 variant which is four redirects the return directives 00:40.630 --> 00:45.650 behaviour changes in it then except a you are dry as the second parameter. 00:45.970 --> 00:46.650 A You are right. 00:46.660 --> 00:49.360 To which the client should be redirected. 00:49.360 --> 00:56.700 For example at the moment we can access the demo sites image by requesting thumb dot P in G. 00:57.100 --> 01:04.600 But let's say we also want to serve this image for Slash logo which obviously right now returns a foro 01:04.600 --> 01:09.620 for we can create a simple redirect using the return directive. 01:09.930 --> 01:12.900 I'll get rid of all these bits from the previous lesson. 01:12.970 --> 01:15.600 Change this location to that slash logo. 01:15.610 --> 01:16.660 You are right. 01:16.960 --> 01:25.500 And in this location return a 3 0 7 so a temporary redirect again or 300 status codes being redirects 01:25.500 --> 01:26.830 of some sort. 01:26.950 --> 01:30.060 And what we want to return is slash thumb. 01:30.070 --> 01:31.720 Dot P in G. 01:31.720 --> 01:33.370 We could also have made this a complete. 01:33.370 --> 01:36.150 You are right with protocol host etc.. 01:36.370 --> 01:41.830 But a relative you are I will be fine as this is redirecting to the same host as the request this coming 01:41.830 --> 01:50.380 from save this reload the configuration and now when we reload this request for Slash logo we get the 01:50.380 --> 01:52.280 thumb doppie G image. 01:52.570 --> 01:58.050 But very importantly note that the u r l changed to thumb don't be in G. 01:58.210 --> 02:04.270 Which is essentially the main difference between rewrites and redirects a redirect simply tells the 02:04.270 --> 02:05.730 client performing the request. 02:05.740 --> 02:08.610 Where to go instead a rewrite. 02:08.620 --> 02:12.240 On the other hand mutates the you are right internally. 02:12.310 --> 02:18.730 So let's see an example this time in the server context before matching the request to any location 02:18.730 --> 02:19.910 contexts. 02:20.050 --> 02:22.070 We can say rewrite. 02:22.240 --> 02:26.280 Pass a regular expression with which to match the you are I. 02:26.500 --> 02:34.540 I'll say Carrott So starting with Slash user slash and then W. plus. 02:34.750 --> 02:42.100 So more than one word character with the second argument being the new you are try to rewrite this to 02:42.550 --> 02:44.540 slash greet. 02:44.550 --> 02:47.940 Now here's the important thing to understand about rewrites. 02:48.190 --> 02:55.630 When you are IE is rewritten it also gets re-evaluated by engine X as a completely new request meaning 02:55.690 --> 02:57.280 at this point here. 02:57.520 --> 03:04.020 The rewritten greet you are I start to right from the top again and will get re-evaluated again. 03:04.210 --> 03:11.380 The re-evaluation makes rewrites very powerful but also requires more system resources than say a return. 03:11.380 --> 03:14.680 Just something to keep in mind when creating rewrite rules. 03:14.890 --> 03:21.700 Okay once rewritten to slash greet this request will move past this rewrite so let's create a location 03:21.700 --> 03:23.170 to match add on. 03:23.170 --> 03:34.030 I'll change this one and return a simple 200 worth Hello user save reload the configuration. 03:34.030 --> 03:36.460 Keeping in mind what our rewrite checks for. 03:36.460 --> 03:43.210 I'll request slash user slash the first part of that rewrite rule John. 03:43.240 --> 03:45.700 The second part with the word match. 03:45.940 --> 03:46.670 Enter. 03:46.960 --> 03:48.520 Hello user. 03:48.520 --> 03:55.570 So clearly the response from slash greet although the browser is still pointing to slash user slash 03:55.570 --> 04:02.290 John meaning the request was rewritten internally only unbeknownst to the client. 04:02.290 --> 04:08.130 Another important and powerful feature of rewrites is the ability to capture certain parts of the original. 04:08.130 --> 04:09.010 You are right. 04:09.340 --> 04:15.840 Using standard regular expression capture groups or example let's say we want to capture a user name. 04:15.940 --> 04:22.870 This word character section of the regular expression simply wrap that part in braces like so. 04:23.110 --> 04:29.320 Which being the first capshaw group in this you are they can be accessed as dollar signs so a variable 04:29.500 --> 04:32.960 one should we have had a second caption Ruby here. 04:32.980 --> 04:38.990 Like this we could have access that value as dollar sign too and so on. 04:38.990 --> 04:46.000 OK so with this variant we're now requesting slash user slash John as we did in the browser and then 04:46.000 --> 04:52.570 rewriting that to slash greet slash John as that will be the value of this capture group. 04:52.570 --> 04:58.990 We can test this by creating an exact match location specifically for Slash greet slash John meaning 04:59.050 --> 05:03.600 any other user will be matched on the standard prefix match and only John. 05:03.710 --> 05:08.860 This exact match returned 200 Hello John. 05:09.800 --> 05:11.730 Reload these changes. 05:11.730 --> 05:18.980 And now what should happen when I refresh this is that slash user slash John should get rewritten to 05:18.980 --> 05:27.320 slash greet slash John revaluated as that new you are II so skipping past the rewrite and then even 05:27.320 --> 05:33.620 though this slash Greek location is a match I was slash greets slash John exact match will take priority 05:33.650 --> 05:34.320 and return. 05:34.340 --> 05:35.370 Hello John. 05:36.080 --> 05:37.020 Test it. 05:37.780 --> 05:39.300 And it works. 05:39.310 --> 05:40.800 Change this to any other user. 05:40.810 --> 05:41.780 However. 05:41.800 --> 05:42.640 Jane. 05:43.400 --> 05:46.110 And we get the prefix match with Hello user. 05:47.390 --> 05:48.800 Get the last part of rewrites. 05:48.810 --> 05:55.860 I'm going to cover is passing optional flags or one in particular the last flag to demonstrate. 05:55.880 --> 05:57.750 OK read another rewrite here. 05:57.840 --> 06:04.550 This time matching slash greet slash John and rewriting it to thumb dot B in G. 06:04.590 --> 06:06.220 The demo site image. 06:06.540 --> 06:13.260 Meaning that if we now request slash user slash John this first rewrite will matchett rewrite it to 06:13.260 --> 06:20.010 slash graetz lashed John and then have it re-evaluate it where it will then match the second rewrite 06:20.070 --> 06:28.350 and again be rewritten to thumb doppie in G and finally served as thumb dont be in G save and test this. 06:30.410 --> 06:32.170 Request John again. 06:33.930 --> 06:39.140 And sure enough we get the thumb image under this user slash John request. 06:39.160 --> 06:44.670 Now what the last flag allows us to do is essentially tell engine X not to allow you are right to be 06:44.670 --> 06:49.510 rewritten any more on this first rewrite add lost. 06:49.560 --> 06:54.960 So still re-evaluate the new you are right after the rewrite but make sure this is the last time it 06:54.960 --> 07:03.140 gets rewritten meaning it should skip over the second rewrite save reload request that same you are 07:03.140 --> 07:06.560 row with a reload and we're back to hello John. 07:07.680 --> 07:10.170 That wraps up redirects and rewrites. 07:10.200 --> 07:16.700 Although technically there's a third kind of rewrite called Try files which will cover in the next lesson.