1 00:00:01,190 --> 00:00:06,410 Regular expressions are used for pattern matching from the beginning. 2 00:00:06,530 --> 00:00:12,310 It can look similar to a wild card but there are quite a big differences. 3 00:00:12,320 --> 00:00:20,000 Regular expressions can be used to much for example email address or IP address and are usually used 4 00:00:20,390 --> 00:00:21,590 among scripts. 5 00:00:21,650 --> 00:00:26,340 So let's check how it looks like here. 6 00:00:26,400 --> 00:00:30,220 They have symbols which are used for regular expression. 7 00:00:30,640 --> 00:00:36,490 Start the differences define dot represents any single character. 8 00:00:36,590 --> 00:00:50,670 So for example more dot K Menchie's bog or for example bar one key next symbol is asterisk and it is 9 00:00:50,670 --> 00:00:54,870 really confusing when you know wildcards meaning of asterisk. 10 00:00:55,260 --> 00:01:00,170 It means that preceding item must match 0 or more times. 11 00:01:00,480 --> 00:01:04,700 So call asterisk now matches. 12 00:01:04,730 --> 00:01:11,010 See how he has because that all it can be match zero times. 13 00:01:11,010 --> 00:01:12,390 This is correct. 14 00:01:12,900 --> 00:01:17,240 Then it also matches goal goal and so on 15 00:01:20,080 --> 00:01:24,190 stat of the line is represented by card. 16 00:01:24,370 --> 00:01:26,290 So card Hello Michie's. 17 00:01:26,360 --> 00:01:35,000 Well I'm starting with Hello similarily end of the line is represented by dollar sign. 18 00:01:35,000 --> 00:01:40,180 So hello dollar sign Michie's line ending with Hello. 19 00:01:40,990 --> 00:01:45,240 Square brackets are the same as for wild cards. 20 00:01:45,550 --> 00:01:55,150 Any one of character Ingo's in square brackets when we use arr. inside square brackets for example file 21 00:01:55,180 --> 00:02:03,380 one Desch the images file one file to Vios three do remember on wild wildcard. 22 00:02:03,380 --> 00:02:06,750 Exclamation mark inside brackets. 23 00:02:06,770 --> 00:02:10,400 Here it is the same situation except the one offering. 24 00:02:10,580 --> 00:02:13,530 Instead of exclamation mark we are using. 25 00:02:13,590 --> 00:02:19,460 Correct and it means any character except those enclosed in brackets. 26 00:02:19,790 --> 00:02:34,160 So file an inside square brackets get 0 1 2 3 4 5 6 7 Menchie's file 8 and file 9 next symbol is a question 27 00:02:34,160 --> 00:02:35,320 mark. 28 00:02:35,360 --> 00:02:48,260 It means that the preceding item must match 1 or 0 times so call question mark hour would match. 29 00:02:48,450 --> 00:02:52,770 Core core but not core. 30 00:02:52,870 --> 00:02:54,000 With W. 31 00:02:55,810 --> 00:03:05,110 Days go to mention that regular expression are not so easy in general and many people are learning them 32 00:03:05,170 --> 00:03:06,260 more than month. 33 00:03:06,340 --> 00:03:08,290 So don't be afraid of them. 34 00:03:08,430 --> 00:03:12,270 Once we will practice it it will be much easier. 35 00:03:14,570 --> 00:03:23,690 If preceding item must match one or more times we should use symbol plus five. 36 00:03:23,710 --> 00:03:38,550 One plus then match file 1 file 11 file 108 11 but not file number inside curly brackets it means that 37 00:03:38,580 --> 00:03:42,780 preceding item must match end times. 38 00:03:42,780 --> 00:03:51,900 That means if we have a range 0 2 9 and in curly brackets number three it would match any three digit 39 00:03:51,960 --> 00:03:59,450 number as one hundred eleven 256 and so on. 40 00:04:00,170 --> 00:04:05,460 And very similar to use in the curly bracket number with comma. 41 00:04:05,820 --> 00:04:11,680 Which means that preceding item should match the minimum number of times. 42 00:04:12,030 --> 00:04:22,490 So in our example it would match any serie or more digit number when we specify to number in the curly 43 00:04:22,490 --> 00:04:23,200 brackets. 44 00:04:23,270 --> 00:04:30,260 We are specifying minimum and maximum number of times the preceding item should match. 45 00:04:30,560 --> 00:04:41,480 So if we specify a range 0 2 9 and inside curly brackets we have numbers 1 and 3 Demetri's or one two 46 00:04:41,570 --> 00:04:43,560 or three digit number. 47 00:04:45,150 --> 00:04:47,840 Last symbol here is backslash. 48 00:04:47,950 --> 00:04:51,390 We are using it as an escape character. 49 00:04:51,610 --> 00:04:55,630 It will escape any of the special character to. 50 00:04:55,780 --> 00:04:58,420 Ignore the meaning of them. 51 00:04:58,800 --> 00:05:03,360 Of course we can use character classes and then use it. 52 00:05:03,360 --> 00:05:06,750 Don't forget to wrap it inside square brackets. 53 00:05:06,750 --> 00:05:11,930 That means that you would have Debro square brackets. 54 00:05:11,930 --> 00:05:17,430 Now let's check how to override the rejects in the script. 55 00:05:18,100 --> 00:05:26,170 If you want to know if string matches some rec X we are using the following double square brackets and 56 00:05:26,230 --> 00:05:35,480 inside some string variable then equal sign for Dubai Guilder and then Reg's a variable. 57 00:05:35,530 --> 00:05:37,970 And don't forget on spaces here. 58 00:05:40,280 --> 00:05:52,010 Now we can see the x example has also some cool feature for matching red X for example beshe rematch 59 00:05:52,400 --> 00:05:55,240 0 matches part of the string. 60 00:05:55,400 --> 00:06:07,100 Which match Reg x 4 part of string which matches HOERR I guess you can also use a variable image and 61 00:06:07,280 --> 00:06:08,500 beshe rematch. 62 00:06:08,510 --> 00:06:17,840 One match is part of the string which is represented as everything inside the exits in close parentheses. 63 00:06:18,440 --> 00:06:20,810 So how do you feel now. 64 00:06:20,810 --> 00:06:27,800 I think the best would be to write some script to see it in action and ensure that there is no magic 65 00:06:27,800 --> 00:06:28,380 at all.