WEBVTT 00:00.450 --> 00:03.650 Now let's look at how to read the input. 00:03.720 --> 00:09.320 Back in ands it's going to be a little bit more involved. 00:09.350 --> 00:23.330 So for this we're going to use the I am stream object of stringy ice cream type file 00:26.090 --> 00:29.330 in just like before we left you open the file 00:35.410 --> 00:38.870 read back in test text that we made last time 00:42.300 --> 00:47.680 and here we're going to check to see if we could open the file. 00:47.760 --> 00:56.860 So how you do as you say is open like this because what if maybe the file doesn't exist. 00:56.940 --> 00:58.230 So you couldn't open it. 00:58.280 --> 00:59.550 In that case. 00:59.760 --> 01:02.870 So we always have to check to see if our files open. 01:02.880 --> 01:07.050 We should be doing this with her out files as well. 01:08.720 --> 01:21.810 So here now what we want to do is actually figure out how big the file is and and you can really think 01:21.810 --> 01:37.560 of files as one big long array and that array will have a cursor where to where it currently points 01:37.560 --> 01:37.890 to. 01:37.890 --> 01:48.220 So you kind of think of it as one big one big array of bytes and the cursor really points to the current 01:48.220 --> 01:49.170 byte. 01:49.390 --> 01:55.870 So when you open the file the cursor is at the very start of the file. 01:56.110 --> 02:03.600 So we want to essentially move the cursor to the end of the file. 02:03.910 --> 02:08.610 Ok so how you do that as a Sikh. 02:09.080 --> 02:16.730 JE zero in five dot and. 02:16.980 --> 02:21.150 So this line will actually move the cursor of the file 02:25.150 --> 02:27.470 to the end of the 02:32.180 --> 02:35.220 Am i asking why you want to do that. 02:35.280 --> 02:35.970 OK. 02:36.240 --> 02:37.950 And this is the reason. 02:38.070 --> 02:42.900 So here now we can actually get how big the file is. 02:42.900 --> 02:51.130 In general I saying infile dot TLG. 02:51.210 --> 02:59.040 So this is actually what TLG does will return the position of the current character in The File. 02:59.100 --> 03:07.560 And since we know that it's at the end this will essentially give us how big the file is and bytes because 03:08.520 --> 03:11.940 it'll start at the first bite at the start. 03:11.940 --> 03:15.710 When you open the file and then you'll seek to the end of the file. 03:15.870 --> 03:24.750 Ok so the cursor is at the very end and TLG will actually tell you what what position the current character 03:24.840 --> 03:26.520 is in the file. 03:26.700 --> 03:28.590 So each character is one byte. 03:28.680 --> 03:32.630 So this will actually give you the entire length of the file. 03:34.250 --> 03:39.250 So now we want to actually read from it again. 03:39.290 --> 03:50.050 So we should actually put the cursor back to the start that by saying zero in filed the beginning. 03:51.320 --> 04:12.270 This will move the cursor you the starch and this will again give the current character or the position 04:12.270 --> 04:21.800 of the current character. 04:21.830 --> 04:26.170 So hopefully this makes sense what's happening here. 04:26.210 --> 04:34.490 So we're moving the cursor of the file every file has a cursor to the very end of the file. 04:34.800 --> 04:35.410 OK. 04:35.660 --> 04:41.870 And then we're getting the current position of the end of the file which really just gives you how many 04:41.870 --> 04:44.010 bytes there are in the file. 04:44.060 --> 04:45.460 This is what this really does. 04:45.480 --> 04:46.620 Second line. 04:46.970 --> 04:52.050 And then we're just moving the cursor back to the start of the file. 04:52.880 --> 04:59.780 And we did all that because we needed the length of the file and we need the length of the file because 04:59.780 --> 05:07.760 we need to know how much to store in our array. 05:08.370 --> 05:20.230 And we're going to make it dynamically and B link plus one can and then using the infile again. 05:20.530 --> 05:29.440 We'll use the get method and actually use this get method for in hangman if you remember to get an entire 05:29.440 --> 05:30.840 C string. 05:31.030 --> 05:33.030 So that's essentially what we're doing here. 05:34.770 --> 05:38.540 We're just getting this E-string of this link. 05:40.550 --> 05:46.380 So this is actually put all all the contents of the file into our new buffer that we created. 05:46.700 --> 05:50.190 So this is the power of dynamic memory. 05:50.360 --> 05:55.350 We have no idea how big the file is in the first place but we can figure it out. 05:55.370 --> 06:03.530 And then just create a buffer to or an array to store it all day. 06:03.740 --> 06:12.080 And then once we get it we'll just put it and this time we actually will use out. 06:12.190 --> 06:17.530 And if you remember that actually we'll put the null character in at the end. 06:17.790 --> 06:21.100 And that's why we have length plus one here 06:23.810 --> 06:37.060 and I'll put it in and we'll actually just delete our buffer array and we'll close the file here. 06:44.100 --> 06:55.140 So if we run this hopefully this will actually output what we input into the file last time we run it 06:55.710 --> 06:56.820 like this. 06:57.040 --> 06:58.100 Hello file. 06:58.180 --> 07:01.830 So. 07:01.860 --> 07:07.550 So hopefully all this made sense and that's a little bit more complicated. 07:07.830 --> 07:14.550 But really this just gives you the length of file or how many bytes the file is. 07:14.850 --> 07:17.190 There should be no surprise to you right. 07:17.280 --> 07:23.710 We're just creating a buffer to put all the characters of the file into. 07:23.760 --> 07:28.410 So this will store all the characters of the buffer and we just read it. 07:28.590 --> 07:31.170 And this is what this getline does. 07:31.170 --> 07:32.220 And we just read 07:35.540 --> 07:40.680 read all the characters in the file and then put all those characters into this buffer. 07:40.960 --> 07:41.750 OK. 07:41.910 --> 07:45.000 And then we just put the buffer delete it and then close the file. 07:45.110 --> 07:49.210 So that's really it for reading. 07:49.410 --> 07:51.060 OK. 07:51.220 --> 08:00.200 And we'll be going over more examples of reading texts in in future lectures. 08:00.790 --> 08:05.290 But in the next lecture I want to go over binary files.