1 00:00:00,240 --> 00:00:03,600 In this lesson we're going to talk about coding in Bash. 2 00:00:03,600 --> 00:00:05,790 Now Bash is the first one we're going to cover 3 00:00:05,790 --> 00:00:09,120 because it comes installed by default inside every 4 00:00:09,120 --> 00:00:11,490 Linux distribution you're going to come across. 5 00:00:11,490 --> 00:00:14,040 Bash is a command line scripting language 6 00:00:14,040 --> 00:00:17,250 that's used for the command shell inside Unix-like systems, 7 00:00:17,250 --> 00:00:20,250 including Linux and Mac OS. 8 00:00:20,250 --> 00:00:21,690 Now if you're familiar with Linux 9 00:00:21,690 --> 00:00:24,240 and you've done some command line programming before, 10 00:00:24,240 --> 00:00:26,610 you're probably really used to using the Bash shell 11 00:00:26,610 --> 00:00:28,830 to be able to execute those commands. 12 00:00:28,830 --> 00:00:30,240 As a scripting language, 13 00:00:30,240 --> 00:00:33,240 Bash is extremely useful when you're automating tasks 14 00:00:33,240 --> 00:00:36,420 that use command line environments inside of Unix. 15 00:00:36,420 --> 00:00:38,460 If you want to be able to call things like Nmap, 16 00:00:38,460 --> 00:00:39,330 for example, 17 00:00:39,330 --> 00:00:41,760 you can do that using Bash shell scripts, 18 00:00:41,760 --> 00:00:44,010 because they already know how to interact with those 19 00:00:44,010 --> 00:00:47,430 different tools that are installed on your Linux system. 20 00:00:47,430 --> 00:00:50,160 The one big limitation when scripting in Bash 21 00:00:50,160 --> 00:00:52,770 is that it is not an object oriented language. 22 00:00:52,770 --> 00:00:55,560 So you are a little bit more limited when you're using Bash 23 00:00:55,560 --> 00:00:58,680 for scripting than you are in other languages like Python, 24 00:00:58,680 --> 00:00:59,513 Pearl, 25 00:00:59,513 --> 00:01:00,346 Ruby, 26 00:01:00,346 --> 00:01:01,179 PowerShell, 27 00:01:01,179 --> 00:01:02,400 or JavaScript. 28 00:01:02,400 --> 00:01:05,910 Now in this lesson we're going to go through some basic Bash, 29 00:01:05,910 --> 00:01:08,640 syntax and commands that you may come across 30 00:01:08,640 --> 00:01:11,040 as you're working with Bash scripts. 31 00:01:11,040 --> 00:01:11,873 First, 32 00:01:11,873 --> 00:01:14,340 anytime you start looking at a Bash script, 33 00:01:14,340 --> 00:01:16,740 it should always start out with the same line. 34 00:01:16,740 --> 00:01:21,740 And this is hashtag bang slash bin slash bash. 35 00:01:21,750 --> 00:01:24,390 This means you're going to see that hashtag, 36 00:01:24,390 --> 00:01:26,760 which normally signifies a comment line 37 00:01:26,760 --> 00:01:29,310 and then the bang or exclamation mark, 38 00:01:29,310 --> 00:01:31,560 then slash bin slash bash, 39 00:01:31,560 --> 00:01:33,720 which says this is a Bash script 40 00:01:33,720 --> 00:01:36,750 and it should be executed using the Bash shell. 41 00:01:36,750 --> 00:01:39,630 From there you're then going to have whatever else you want 42 00:01:39,630 --> 00:01:43,140 coded into that script for what you want to do. 43 00:01:43,140 --> 00:01:44,850 Now if you're looking at a script 44 00:01:44,850 --> 00:01:46,770 and you're trying to figure out if it's a Bash script, 45 00:01:46,770 --> 00:01:48,480 what's the first thing you should look at? 46 00:01:48,480 --> 00:01:49,313 That's right, 47 00:01:49,313 --> 00:01:51,030 you should look at the first line. 48 00:01:51,030 --> 00:01:55,080 If it has hashtag bang slash bin slash bash, 49 00:01:55,080 --> 00:01:56,772 you know it's a Bash script. 50 00:01:56,772 --> 00:02:00,210 Now any other time you see that hashtag 51 00:02:00,210 --> 00:02:02,910 you should remember that this is a comment. 52 00:02:02,910 --> 00:02:06,150 Now this holds true in many different programming languages, 53 00:02:06,150 --> 00:02:06,983 Bash, 54 00:02:06,983 --> 00:02:07,816 Python, 55 00:02:07,816 --> 00:02:08,649 Ruby, 56 00:02:08,649 --> 00:02:11,610 and PowerShell all use the syntax of a hashtag 57 00:02:11,610 --> 00:02:14,010 to signify everything beyond that hashtag 58 00:02:14,010 --> 00:02:17,310 is going to be ignored by the scripting engine or compiler 59 00:02:17,310 --> 00:02:19,830 because it's just a human readable comment. 60 00:02:19,830 --> 00:02:21,690 So I might say, 61 00:02:21,690 --> 00:02:22,710 hashtag, 62 00:02:22,710 --> 00:02:24,810 this is the first line of my script. 63 00:02:24,810 --> 00:02:26,400 And that just tells people that that's 64 00:02:26,400 --> 00:02:27,990 the first line of my script, 65 00:02:27,990 --> 00:02:31,140 or I might tell them exactly what this script is used for. 66 00:02:31,140 --> 00:02:34,530 Maybe it's hashtag this script is used to do backups 67 00:02:34,530 --> 00:02:35,790 of my systems. 68 00:02:35,790 --> 00:02:37,470 Something like that. 69 00:02:37,470 --> 00:02:39,870 The next thing we need to talk about inside of Bash 70 00:02:39,870 --> 00:02:41,760 is the idea of variables. 71 00:02:41,760 --> 00:02:43,980 Now we've talked generally about variables before 72 00:02:43,980 --> 00:02:45,897 and how they're used to represent any value 73 00:02:45,897 --> 00:02:48,090 and that they can be changed during the execution 74 00:02:48,090 --> 00:02:49,470 of the program. 75 00:02:49,470 --> 00:02:53,430 For Bash you can declare a variable by using the variable 76 00:02:53,430 --> 00:02:56,850 name equals and the thing you want it to be. 77 00:02:56,850 --> 00:02:57,780 For example, 78 00:02:57,780 --> 00:03:00,960 if I did customer name equals Jason, 79 00:03:00,960 --> 00:03:04,500 that would now define that variable customer name 80 00:03:04,500 --> 00:03:05,850 as a variable. 81 00:03:05,850 --> 00:03:08,500 Now anytime I want to call that customer name variable, 82 00:03:08,500 --> 00:03:10,560 I'm not going to write customer name, 83 00:03:10,560 --> 00:03:14,040 instead I'm going to use dollar sign customer name 84 00:03:14,040 --> 00:03:15,608 and the dollar sign customer name says, 85 00:03:15,608 --> 00:03:19,410 I want to call the variable known as customer name. 86 00:03:19,410 --> 00:03:21,000 So when you're assigning something, 87 00:03:21,000 --> 00:03:22,380 there's no dollar sign. 88 00:03:22,380 --> 00:03:23,370 When you're calling it, 89 00:03:23,370 --> 00:03:25,110 there is a dollar sign. 90 00:03:25,110 --> 00:03:27,210 Also notice that I use a syntax 91 00:03:27,210 --> 00:03:29,700 of uppercase and lowercase letters here, 92 00:03:29,700 --> 00:03:32,910 generally in Bash and a lot of our other naming schemes, 93 00:03:32,910 --> 00:03:36,000 we will call things as variables using title case 94 00:03:36,000 --> 00:03:37,830 where the first letter is capitalized 95 00:03:37,830 --> 00:03:39,870 and the rest of the word is lowercase. 96 00:03:39,870 --> 00:03:41,280 This just makes it easier to read 97 00:03:41,280 --> 00:03:43,050 when I have double name words, 98 00:03:43,050 --> 00:03:44,160 like customer name, 99 00:03:44,160 --> 00:03:46,650 being used as a single variable. 100 00:03:46,650 --> 00:03:48,930 In Bash when you declare your variable, 101 00:03:48,930 --> 00:03:51,240 you can also type that variable. 102 00:03:51,240 --> 00:03:53,850 Now typing is where you declare a specific function 103 00:03:53,850 --> 00:03:55,470 essentially for that variable. 104 00:03:55,470 --> 00:03:56,700 Is it going to be a string, 105 00:03:56,700 --> 00:03:57,810 a numeric array, 106 00:03:57,810 --> 00:03:58,643 a number, 107 00:03:58,643 --> 00:04:00,060 or something like that. 108 00:04:00,060 --> 00:04:01,590 Essentially to do this, 109 00:04:01,590 --> 00:04:04,830 you're going to do declare option the variable name 110 00:04:04,830 --> 00:04:06,450 equals the value. 111 00:04:06,450 --> 00:04:07,440 So for example, 112 00:04:07,440 --> 00:04:10,230 if I wanted to create a variable called phone number 113 00:04:10,230 --> 00:04:12,480 and I wanted it to be treated as a number, 114 00:04:12,480 --> 00:04:13,920 I can declare it by saying, 115 00:04:13,920 --> 00:04:18,660 declare dash I then phone number equals 116 00:04:18,660 --> 00:04:22,620 and whatever value I want like 1, 1, 1, 1, 1, 1, 1. 117 00:04:22,620 --> 00:04:24,660 This is now my seven digit phone number 118 00:04:24,660 --> 00:04:27,030 and it will be treated as a number. 119 00:04:27,030 --> 00:04:29,070 Now if you want to make something a constant 120 00:04:29,070 --> 00:04:30,510 where it's not going to change, 121 00:04:30,510 --> 00:04:32,460 such as the definition of Pi, 122 00:04:32,460 --> 00:04:35,310 we can do that by again using the declare option. 123 00:04:35,310 --> 00:04:40,310 We're going to do declare dash r Pi equals 3.14. 124 00:04:41,340 --> 00:04:42,330 In this case, 125 00:04:42,330 --> 00:04:44,520 I made that variable read only, 126 00:04:44,520 --> 00:04:45,353 or in other words, 127 00:04:45,353 --> 00:04:48,720 it became a constant because I can't change it again. 128 00:04:48,720 --> 00:04:51,660 The next thing we need to understand is how to use arrays 129 00:04:51,660 --> 00:04:53,280 inside of Bash. 130 00:04:53,280 --> 00:04:55,440 Now if I want to create an array in Bash, 131 00:04:55,440 --> 00:04:58,440 I'm simply going to give it a name like I would a variable. 132 00:04:58,440 --> 00:05:02,370 So I might use something like tempArray equals 133 00:05:02,370 --> 00:05:04,980 and then I want to put all of the things it's going to equal 134 00:05:04,980 --> 00:05:07,800 inside of parenthesis and separate it by commas. 135 00:05:07,800 --> 00:05:12,800 So tempArray equals parenthesis value1 comma value two 136 00:05:12,810 --> 00:05:14,550 comma value three. 137 00:05:14,550 --> 00:05:17,400 Now I have an array with three different items in it 138 00:05:17,400 --> 00:05:20,640 listed as value one, two, and three. 139 00:05:20,640 --> 00:05:22,590 If you want to get information stored in an array 140 00:05:22,590 --> 00:05:24,270 back out inside of Bash, 141 00:05:24,270 --> 00:05:27,030 you're simply going to refer to it as dollar sign, 142 00:05:27,030 --> 00:05:27,900 the array, 143 00:05:27,900 --> 00:05:29,850 bracket and the position number. 144 00:05:29,850 --> 00:05:33,570 So in the case of my temporary array with my three values, 145 00:05:33,570 --> 00:05:35,209 if I wanted to pull out value two, 146 00:05:35,209 --> 00:05:37,050 I would use dollar sign, 147 00:05:37,050 --> 00:05:40,536 tempArray bracket one end bracket. 148 00:05:40,536 --> 00:05:42,870 This would then be able to give me the value 149 00:05:42,870 --> 00:05:46,350 from position number two because we count from zero, 150 00:05:46,350 --> 00:05:47,183 then one, 151 00:05:47,183 --> 00:05:49,020 then two inside of computers, 152 00:05:49,020 --> 00:05:51,390 and that would give me value two back as the thing 153 00:05:51,390 --> 00:05:52,980 I'm referencing. 154 00:05:52,980 --> 00:05:56,610 Next we have named arrays and associative arrays. 155 00:05:56,610 --> 00:05:59,790 this almost like a table inside of a database. 156 00:05:59,790 --> 00:06:01,710 And any data stored in this array 157 00:06:01,710 --> 00:06:03,336 is now going to be based on names. 158 00:06:03,336 --> 00:06:06,994 So in Bash I do this by having to declare the array, 159 00:06:06,994 --> 00:06:08,637 using a specific type. 160 00:06:08,637 --> 00:06:11,670 And that type is dash capital A. 161 00:06:11,670 --> 00:06:13,560 Let's go ahead and declare a named array 162 00:06:13,560 --> 00:06:16,230 or associative array inside of Bash. 163 00:06:16,230 --> 00:06:19,770 To do this I'm going to use declare dash capital A 164 00:06:19,770 --> 00:06:21,030 and then the array name, 165 00:06:21,030 --> 00:06:21,863 in my case, 166 00:06:21,863 --> 00:06:23,664 I'm going to call it phone book. 167 00:06:23,664 --> 00:06:27,030 Now when I want to get information into that 168 00:06:27,030 --> 00:06:29,976 I'm simply going to go ahead and say phone book bracket, 169 00:06:29,976 --> 00:06:31,920 and the key I want to use, 170 00:06:31,920 --> 00:06:32,837 let's say name. 171 00:06:32,837 --> 00:06:36,240 Then I'm going to equal that to the name I want to store 172 00:06:36,240 --> 00:06:38,040 such as Jason. 173 00:06:38,040 --> 00:06:40,410 Then if I want to put additional information in there, 174 00:06:40,410 --> 00:06:42,840 I can simply do something like phone book, 175 00:06:42,840 --> 00:06:45,720 bracket number equals, 176 00:06:45,720 --> 00:06:49,380 then the number 111 dash 1111. 177 00:06:49,380 --> 00:06:51,888 Now if I want to get information back out of this array, 178 00:06:51,888 --> 00:06:56,700 I can do it by doing dollar sign curly brace phone book 179 00:06:56,700 --> 00:07:00,180 bracket name bracket curly brace, 180 00:07:00,180 --> 00:07:02,190 and this will then give me the information back out, 181 00:07:02,190 --> 00:07:04,980 such as the name which was Jason. 182 00:07:04,980 --> 00:07:07,020 If I wanted to get the phone number back out, 183 00:07:07,020 --> 00:07:10,653 I would simply use dollar sign curly bracket hone book, 184 00:07:11,726 --> 00:07:13,743 bracket number bracket curly brace, 185 00:07:14,640 --> 00:07:18,480 and then number will come back out as 111 dash 1111, 186 00:07:18,480 --> 00:07:20,760 which was the phone number I stored in there. 187 00:07:20,760 --> 00:07:23,460 This essentially is storing these key value pairs 188 00:07:23,460 --> 00:07:25,260 inside of the array for us. 189 00:07:25,260 --> 00:07:28,713 And this is a way that we can use these associative arrays. 190 00:07:29,640 --> 00:07:33,840 Next let's talk about doing comparisons inside of Bash. 191 00:07:33,840 --> 00:07:36,420 Flow controls are going to be based on doing some kind of a 192 00:07:36,420 --> 00:07:39,660 comparison like is something equal or not equal 193 00:07:39,660 --> 00:07:40,620 or greater than, 194 00:07:40,620 --> 00:07:42,210 or greater than or equal to, 195 00:07:42,210 --> 00:07:43,043 less than, 196 00:07:43,043 --> 00:07:44,160 less than or equal to, 197 00:07:44,160 --> 00:07:45,690 and things like that. 198 00:07:45,690 --> 00:07:49,290 Now when we're doing arithmetic comparisons inside of Bash, 199 00:07:49,290 --> 00:07:51,370 we're normally going to use text to signify that 200 00:07:51,370 --> 00:07:54,270 instead of actually using the symbols. 201 00:07:54,270 --> 00:07:55,260 For example, 202 00:07:55,260 --> 00:07:58,590 if I wanted to compare two variables known as A and B, 203 00:07:58,590 --> 00:08:03,420 I can do that by doing if bracket quote dollar sign a 204 00:08:03,420 --> 00:08:08,420 quote dash eq quote dollar sign b quote bracket. 205 00:08:09,180 --> 00:08:11,610 This says is a equal to b. 206 00:08:11,610 --> 00:08:12,443 If it is, 207 00:08:12,443 --> 00:08:13,980 it returns a value of one. 208 00:08:13,980 --> 00:08:14,813 If it's not, 209 00:08:14,813 --> 00:08:16,920 it returns a value of zero. 210 00:08:16,920 --> 00:08:19,770 Now if I wanted to check if two things are not equal, 211 00:08:19,770 --> 00:08:22,290 I can do that by using dash ne. 212 00:08:22,290 --> 00:08:27,030 So it would be if dollar sign a dash ne dollar sign b, 213 00:08:27,030 --> 00:08:30,330 that's going to check is a not equal to b. 214 00:08:30,330 --> 00:08:31,680 So if a and b are equal, 215 00:08:31,680 --> 00:08:33,330 I will get a zero. 216 00:08:33,330 --> 00:08:34,380 If they're not equal, 217 00:08:34,380 --> 00:08:35,580 I'll get a one because this 218 00:08:35,580 --> 00:08:38,100 is basically reverse bullion logic. 219 00:08:38,100 --> 00:08:40,740 If I want to do something as greater than something else 220 00:08:40,740 --> 00:08:43,049 I'm going to use dash gt. 221 00:08:43,049 --> 00:08:44,670 If I want to say is something greater 222 00:08:44,670 --> 00:08:48,960 than or equal to something else I'm going to use dash ge. 223 00:08:48,960 --> 00:08:51,870 If I want less than I'm going to use dash lt. 224 00:08:51,870 --> 00:08:54,690 And if I want to use less than or equal to, 225 00:08:54,690 --> 00:08:56,103 I'm going to use dash le. 226 00:08:57,210 --> 00:08:58,650 Now in addition to this, 227 00:08:58,650 --> 00:09:00,030 in newer versions of Bash, 228 00:09:00,030 --> 00:09:02,400 you can use the arithmetic symbols 229 00:09:02,400 --> 00:09:03,750 such as the less than sign, 230 00:09:03,750 --> 00:09:05,190 the less than equal to, 231 00:09:05,190 --> 00:09:06,023 the greater than, 232 00:09:06,023 --> 00:09:07,890 and the greater than equal to sign. 233 00:09:07,890 --> 00:09:09,810 But when you do that, 234 00:09:09,810 --> 00:09:11,880 you need to use double parentheses 235 00:09:11,880 --> 00:09:13,680 around the thing you're testing. 236 00:09:13,680 --> 00:09:15,300 So instead of saying, 237 00:09:15,300 --> 00:09:20,300 if bracket dollar sign a dash le dollar sign b bracket, 238 00:09:20,820 --> 00:09:24,120 we would then use parenthesis parenthesis dollar sign a 239 00:09:24,120 --> 00:09:27,510 less than dollar sign b parenthesis parenthesis. 240 00:09:27,510 --> 00:09:30,204 This double parenthesis replaces the word if 241 00:09:30,204 --> 00:09:33,960 and those brackets inside of the comparisons. 242 00:09:33,960 --> 00:09:36,810 In addition to being able to compare mathematical things, 243 00:09:36,810 --> 00:09:40,230 we also sometimes need to do comparisons with strings. 244 00:09:40,230 --> 00:09:41,160 For example, 245 00:09:41,160 --> 00:09:42,990 are two strings equal? 246 00:09:42,990 --> 00:09:46,680 Well we can do that if we use the if command. 247 00:09:46,680 --> 00:09:47,513 So again, 248 00:09:47,513 --> 00:09:50,340 we're going to use if bracket dollar sign a 249 00:09:50,340 --> 00:09:52,530 equals dollar sign b bracket. 250 00:09:52,530 --> 00:09:55,710 Notice when we were doing mathematical comparisons, 251 00:09:55,710 --> 00:09:58,315 we were using the dash eq in this format, 252 00:09:58,315 --> 00:10:01,230 but now because we're using the equal sign, 253 00:10:01,230 --> 00:10:04,080 we're doing this as a text string comparison. 254 00:10:04,080 --> 00:10:06,300 This would test something like the word Jason 255 00:10:06,300 --> 00:10:07,770 against the word Jason. 256 00:10:07,770 --> 00:10:10,464 If one had a capital letter and one had a lower case letter, 257 00:10:10,464 --> 00:10:13,050 those two words are not going to be equal, 258 00:10:13,050 --> 00:10:15,900 and we're going to get a zero return by this function. 259 00:10:15,900 --> 00:10:18,060 Now in addition to using a single equal, 260 00:10:18,060 --> 00:10:20,430 you can also use a double equal sign, 261 00:10:20,430 --> 00:10:21,570 and these are equivalent 262 00:10:21,570 --> 00:10:22,950 and it doesn't really make a difference 263 00:10:22,950 --> 00:10:25,440 when you're doing a string comparison. 264 00:10:25,440 --> 00:10:28,380 Now the next thing we have is the not equal to. 265 00:10:28,380 --> 00:10:29,940 If you want to compare two strings 266 00:10:29,940 --> 00:10:32,130 and see if they are not equal to each other, 267 00:10:32,130 --> 00:10:34,380 you can do this by comparing them using 268 00:10:34,380 --> 00:10:39,380 if bracket dollar sign a bang equals dollar sign b bracket, 269 00:10:40,650 --> 00:10:44,130 essentially we are going to use an exclamation equal sign 270 00:10:44,130 --> 00:10:46,445 to mean not equal to. 271 00:10:46,445 --> 00:10:49,530 Next we have the less than and greater than. 272 00:10:49,530 --> 00:10:50,363 And again, 273 00:10:50,363 --> 00:10:54,060 we can compare string text using less than or greater than. 274 00:10:54,060 --> 00:10:56,730 Now you may wonder how do you compare two things 275 00:10:56,730 --> 00:10:57,930 that are words? 276 00:10:57,930 --> 00:11:00,510 Well we do it based on ASCII order. 277 00:11:00,510 --> 00:11:01,440 For example, 278 00:11:01,440 --> 00:11:04,120 if I compare the word Jason to the word Dion, 279 00:11:04,120 --> 00:11:07,890 Jason is greater than Dion because J comes after D 280 00:11:07,890 --> 00:11:09,900 in the ASCII alphabet. 281 00:11:09,900 --> 00:11:14,010 To use these you're going to do if bracket dollar sign a 282 00:11:14,010 --> 00:11:16,884 slash less than dollar sign b bracket. 283 00:11:16,884 --> 00:11:19,860 Notice I had to have that slash there. 284 00:11:19,860 --> 00:11:21,450 This is an escape character 285 00:11:21,450 --> 00:11:23,880 because we are inside a single bracket. 286 00:11:23,880 --> 00:11:26,100 If I didn't want to use that escape character, 287 00:11:26,100 --> 00:11:30,150 I can type it out as if bracket bracket dollar sign a 288 00:11:30,150 --> 00:11:33,570 less than dollar sign b bracket bracket instead, 289 00:11:33,570 --> 00:11:36,600 and that way I don't need to use the escape character. 290 00:11:36,600 --> 00:11:39,870 This same format is also used for the greater than sign, 291 00:11:39,870 --> 00:11:41,580 where you're going to use double brackets 292 00:11:41,580 --> 00:11:44,070 with just the greater than sign or single brackets 293 00:11:44,070 --> 00:11:46,170 and the slash and the greater than sign 294 00:11:46,170 --> 00:11:49,143 when comparing two ASCII strings against each other. 295 00:11:50,070 --> 00:11:53,460 Next we have our logical comparisons inside of Bash. 296 00:11:53,460 --> 00:11:56,880 The most basic form of this is an if then statement. 297 00:11:56,880 --> 00:11:58,980 Inside of Bash you're going to do if, 298 00:11:58,980 --> 00:12:00,510 the condition you're testing, 299 00:12:00,510 --> 00:12:02,156 then the command you want to run, 300 00:12:02,156 --> 00:12:05,070 and then you're going to close it out using fi. 301 00:12:05,070 --> 00:12:07,440 This takes the place of using any kind of brackets 302 00:12:07,440 --> 00:12:10,590 or parentheses inside of these function calls. 303 00:12:10,590 --> 00:12:13,020 Now if you want to do something a little bit more complex, 304 00:12:13,020 --> 00:12:18,020 you can use something like if then elif then else fi. 305 00:12:19,410 --> 00:12:22,410 Now what this means is I'm going to test a first condition, 306 00:12:22,410 --> 00:12:24,240 then do some code if it's true. 307 00:12:24,240 --> 00:12:25,260 If it's not true, 308 00:12:25,260 --> 00:12:27,450 I'm going to go into a second else condition. 309 00:12:27,450 --> 00:12:28,920 I'm going to test that condition. 310 00:12:28,920 --> 00:12:29,970 If it's true, 311 00:12:29,970 --> 00:12:31,020 I'm going to do some code. 312 00:12:31,020 --> 00:12:31,950 If it's not, 313 00:12:31,950 --> 00:12:34,260 then I'm going to do the third option. 314 00:12:34,260 --> 00:12:36,810 Now the next thing we have is our loops 315 00:12:36,810 --> 00:12:39,360 and we call these our four our do while 316 00:12:39,360 --> 00:12:40,560 and our wild commands. 317 00:12:40,560 --> 00:12:42,540 We went through the different flow control options 318 00:12:42,540 --> 00:12:44,010 in an earlier lesson. 319 00:12:44,010 --> 00:12:47,640 Now in Bash we actually term them a little bit different. 320 00:12:47,640 --> 00:12:49,620 When we talk about the four loop, 321 00:12:49,620 --> 00:12:52,710 we are really talking about a four do done, 322 00:12:52,710 --> 00:12:55,290 and that's the statement syntax we're going to use. 323 00:12:55,290 --> 00:12:57,540 When you use a four do done, 324 00:12:57,540 --> 00:12:59,190 you're going to perform a set of commands 325 00:12:59,190 --> 00:13:01,410 for each item in a given list. 326 00:13:01,410 --> 00:13:06,000 This is going to take the form of four variable in list 327 00:13:06,000 --> 00:13:08,670 do some commands done. 328 00:13:08,670 --> 00:13:09,870 So for example, 329 00:13:09,870 --> 00:13:14,250 for value in curly brackets one dot dot five 330 00:13:14,250 --> 00:13:18,300 end curly brackets do echo dollar sign value 331 00:13:18,300 --> 00:13:21,000 done echo all done. 332 00:13:21,000 --> 00:13:23,490 This script is basically going to do counting. 333 00:13:23,490 --> 00:13:26,580 It's going to start out and set the value to one, 334 00:13:26,580 --> 00:13:30,000 and then it's going to echo value of one to the screen. 335 00:13:30,000 --> 00:13:32,940 Next it's going to set it to two and echo that to the screen. 336 00:13:32,940 --> 00:13:33,773 Then three, 337 00:13:33,773 --> 00:13:34,606 then four, 338 00:13:34,606 --> 00:13:35,670 then five. 339 00:13:35,670 --> 00:13:37,200 Once all five are done, 340 00:13:37,200 --> 00:13:39,180 it's then going to go to the final echo command 341 00:13:39,180 --> 00:13:40,650 and say all done. 342 00:13:40,650 --> 00:13:45,510 So what you'll see on the screen is 12345all done. 343 00:13:45,510 --> 00:13:48,720 The second one we have is what's known as a do while. 344 00:13:48,720 --> 00:13:51,570 Now a do while inside a Bash is instead 345 00:13:51,570 --> 00:13:53,940 called a wild do done. 346 00:13:53,940 --> 00:13:57,300 This performs a set of commands while a test is true. 347 00:13:57,300 --> 00:13:58,380 So it's going to take the form 348 00:13:58,380 --> 00:14:02,760 of while some test do some commands done. 349 00:14:02,760 --> 00:14:04,800 Consider the following sample script, 350 00:14:04,800 --> 00:14:08,550 counter equals one while compare the counter variable 351 00:14:08,550 --> 00:14:13,550 less than 10 do echo counter then counter plus plus 352 00:14:14,370 --> 00:14:16,920 done echo all done. 353 00:14:16,920 --> 00:14:17,904 So what is this doing? 354 00:14:17,904 --> 00:14:20,940 Well we're going to start out by setting the counter to one. 355 00:14:20,940 --> 00:14:24,257 Then as long as the variable of counter is less than 10, 356 00:14:24,257 --> 00:14:26,310 we are going to go through this loop. 357 00:14:26,310 --> 00:14:27,143 In this case, 358 00:14:27,143 --> 00:14:28,650 we just set the variable to one, 359 00:14:28,650 --> 00:14:30,540 so one is less than 10. 360 00:14:30,540 --> 00:14:32,940 So we are going to do the echo 361 00:14:32,940 --> 00:14:34,470 or printing something to the screen, 362 00:14:34,470 --> 00:14:35,670 which is the counter. 363 00:14:35,670 --> 00:14:37,380 So we print one to the screen. 364 00:14:37,380 --> 00:14:40,533 Then counter plus plus means take the value of counter, 365 00:14:40,533 --> 00:14:43,740 add one and save it back to the counter variable. 366 00:14:43,740 --> 00:14:45,690 So now my counter is two. 367 00:14:45,690 --> 00:14:46,980 Is two less than 10? 368 00:14:46,980 --> 00:14:47,880 Yes it is. 369 00:14:47,880 --> 00:14:49,200 So we'll print that to the screen. 370 00:14:49,200 --> 00:14:50,520 We'll increment the three. 371 00:14:50,520 --> 00:14:53,310 We'll continue doing that all the way through as we go 372 00:14:53,310 --> 00:14:56,040 through nine it's less than 10 we'll print nine to the 373 00:14:56,040 --> 00:14:58,113 screen we'll increment and now we're at 10. 374 00:14:58,113 --> 00:14:59,670 When we check that, 375 00:14:59,670 --> 00:15:01,350 10 is not less than 10, 376 00:15:01,350 --> 00:15:02,340 so we'll stop. 377 00:15:02,340 --> 00:15:04,110 So what you'll see is a counter. 378 00:15:04,110 --> 00:15:09,110 That's going to print 123456789All done to your screen. 379 00:15:10,290 --> 00:15:12,120 The final one we have in Bash 380 00:15:12,120 --> 00:15:14,100 is going to be the wild command. 381 00:15:14,100 --> 00:15:18,270 And in Bash we actually call this until do done. 382 00:15:18,270 --> 00:15:22,320 This performs a set of commands until a test returns true. 383 00:15:22,320 --> 00:15:27,320 So we'll do until some test do these commands done. 384 00:15:28,350 --> 00:15:29,340 For example, 385 00:15:29,340 --> 00:15:33,060 counter equals one until counter is greater than five 386 00:15:33,060 --> 00:15:38,060 do echo counter counter plus plus done echo all done. 387 00:15:38,076 --> 00:15:41,010 This says we're going to set our counter at one 388 00:15:41,010 --> 00:15:42,990 until the counter is greater than five, 389 00:15:42,990 --> 00:15:44,700 we're going to do everything in the loop. 390 00:15:44,700 --> 00:15:45,840 Since our counter is one, 391 00:15:45,840 --> 00:15:48,210 we're going to echo that counter to the screen. 392 00:15:48,210 --> 00:15:51,090 Then we're going to increment the counter and make it two. 393 00:15:51,090 --> 00:15:52,530 Is two greater than five? 394 00:15:52,530 --> 00:15:53,363 No. 395 00:15:53,363 --> 00:15:54,870 So we're going to keep doing that function. 396 00:15:54,870 --> 00:15:56,190 Echo two to the screen, 397 00:15:56,190 --> 00:15:58,470 make it three is three greater than five? 398 00:15:58,470 --> 00:15:59,303 No. 399 00:15:59,303 --> 00:16:00,330 Print that to the screen. 400 00:16:00,330 --> 00:16:01,590 Is four greater than five? 401 00:16:01,590 --> 00:16:02,423 No. 402 00:16:02,423 --> 00:16:03,270 Print that to the screen. 403 00:16:03,270 --> 00:16:04,560 Is five greater than five? 404 00:16:04,560 --> 00:16:05,393 No. 405 00:16:05,393 --> 00:16:06,450 So print that to the screen. 406 00:16:06,450 --> 00:16:08,100 And then is six now greater than five? 407 00:16:08,100 --> 00:16:08,933 Yes. 408 00:16:08,933 --> 00:16:10,710 We can stop doing that function. 409 00:16:10,710 --> 00:16:13,650 This is the way flow control works inside a Bash 410 00:16:13,650 --> 00:16:16,680 when you're using these different types of controls. 411 00:16:16,680 --> 00:16:20,160 Next we need to talk about some basic string operations. 412 00:16:20,160 --> 00:16:22,320 String operations are the commands that are used 413 00:16:22,320 --> 00:16:25,050 to manipulate data that is of the string format, 414 00:16:25,050 --> 00:16:26,533 things like words. 415 00:16:26,533 --> 00:16:28,590 Now when you're dealing with strings, 416 00:16:28,590 --> 00:16:31,500 you're going to have a variable like test string equals 417 00:16:31,500 --> 00:16:33,810 quote test space string. 418 00:16:33,810 --> 00:16:36,345 That means that variable of test string now contains 419 00:16:36,345 --> 00:16:39,377 the words test space and string. 420 00:16:39,377 --> 00:16:42,420 Now that I have that string stored as test string, 421 00:16:42,420 --> 00:16:44,370 I can display it in multiple ways 422 00:16:44,370 --> 00:16:46,800 by manipulating what is going to be displayed. 423 00:16:46,800 --> 00:16:50,040 If I use the echo command and use dollar sign test string, 424 00:16:50,040 --> 00:16:52,050 it's just going to show me the entire thing, 425 00:16:52,050 --> 00:16:54,030 test space string, 426 00:16:54,030 --> 00:16:57,810 but I can also manipulate that string before displaying it. 427 00:16:57,810 --> 00:16:59,880 Now if I wanted to show a sub string, 428 00:16:59,880 --> 00:17:02,730 I can do that by using positioning inside 429 00:17:02,730 --> 00:17:04,170 of calling that variable. 430 00:17:04,170 --> 00:17:07,710 So let's say I did echo dollar sign curly bracket 431 00:17:07,710 --> 00:17:12,710 test string colon 2 colon 4 end curly bracket. 432 00:17:12,720 --> 00:17:14,130 What does this say? 433 00:17:14,130 --> 00:17:17,430 Well this is saying that I want to start at position two 434 00:17:17,430 --> 00:17:20,010 and I want to count four places from there. 435 00:17:20,010 --> 00:17:24,000 So in my case of using the test string as my variable 436 00:17:24,000 --> 00:17:27,150 with the contents of test space string as my string, 437 00:17:27,150 --> 00:17:29,700 I can now have starting at position two, 438 00:17:29,700 --> 00:17:30,900 which is the S, 439 00:17:30,900 --> 00:17:32,430 I'm going to count four places. 440 00:17:32,430 --> 00:17:35,610 So st space S, 441 00:17:35,610 --> 00:17:37,500 that is what I'm going to show on the screen 442 00:17:37,500 --> 00:17:39,900 when I use this echo command. 443 00:17:39,900 --> 00:17:42,540 There are lots of other ways to do string operations, 444 00:17:42,540 --> 00:17:44,490 and we're just touching the surface here, 445 00:17:44,490 --> 00:17:46,260 but I just wanted to introduce you to the concept 446 00:17:46,260 --> 00:17:47,938 that what you have stored in a variable 447 00:17:47,938 --> 00:17:50,400 can be modified when you display it 448 00:17:50,400 --> 00:17:53,640 or modified and stored back into the variable. 449 00:17:53,640 --> 00:17:55,820 The next thing we need to talk about in terms of Bash 450 00:17:55,820 --> 00:17:58,290 is going to be inputting and outputting data. 451 00:17:58,290 --> 00:18:00,210 You want to take input from the keyboard, 452 00:18:00,210 --> 00:18:01,200 from your user, 453 00:18:01,200 --> 00:18:03,060 and give output back to the monitor 454 00:18:03,060 --> 00:18:04,860 when you want to give them information. 455 00:18:04,860 --> 00:18:07,800 I've already used echo many times in this demonstration, 456 00:18:07,800 --> 00:18:09,150 but echo is the easiest way 457 00:18:09,150 --> 00:18:11,220 to send things back to the monitor. 458 00:18:11,220 --> 00:18:13,243 You simply use echo and the variable 459 00:18:13,243 --> 00:18:17,160 or echo and a quote with whatever string you want to display. 460 00:18:17,160 --> 00:18:18,090 For example, 461 00:18:18,090 --> 00:18:19,365 let's say I wanted to say, 462 00:18:19,365 --> 00:18:22,020 please enter your name on the screen. 463 00:18:22,020 --> 00:18:24,701 So I would do echo quote please enter your name 464 00:18:24,701 --> 00:18:26,820 colon end quote. 465 00:18:26,820 --> 00:18:29,550 That's going to display that string on the screen. 466 00:18:29,550 --> 00:18:31,980 Now if I wanted to read information from you, 467 00:18:31,980 --> 00:18:33,630 I can use the command read 468 00:18:33,630 --> 00:18:36,660 and a variable name such as username. 469 00:18:36,660 --> 00:18:39,240 Now when you enter in your username and hit enter, 470 00:18:39,240 --> 00:18:41,970 it's going to be stored in the variable username. 471 00:18:41,970 --> 00:18:43,950 If I want to display that back to the screen, 472 00:18:43,950 --> 00:18:48,270 I would then type echo quote hello dollar sign username 473 00:18:48,270 --> 00:18:50,460 exclamation point end quote. 474 00:18:50,460 --> 00:18:53,430 And so what this would look like is please enter your name. 475 00:18:53,430 --> 00:18:54,720 I would type in Jason, 476 00:18:54,720 --> 00:18:55,620 hit enter, 477 00:18:55,620 --> 00:18:57,707 and then you would see hello Jason. 478 00:18:57,707 --> 00:19:01,230 That's the idea of input and output to a screen. 479 00:19:01,230 --> 00:19:02,567 Now in addition to inputting and outputting 480 00:19:02,567 --> 00:19:03,960 things to the screen, 481 00:19:03,960 --> 00:19:07,410 you can also read or write data into files. 482 00:19:07,410 --> 00:19:08,820 If you want to do this in Bash, 483 00:19:08,820 --> 00:19:10,110 it's quite simple. 484 00:19:10,110 --> 00:19:11,700 You're going to create a variable name 485 00:19:11,700 --> 00:19:13,320 that's going to act as that file. 486 00:19:13,320 --> 00:19:14,153 For instance, 487 00:19:14,153 --> 00:19:15,120 temp file. 488 00:19:15,120 --> 00:19:18,240 You're going to set that equal to dollar sign parenthesis 489 00:19:18,240 --> 00:19:21,480 less than the file name end parenthesis. 490 00:19:21,480 --> 00:19:23,910 So I might use something like temp file 491 00:19:23,910 --> 00:19:27,330 equals dollar sign parenthesis less than test 492 00:19:27,330 --> 00:19:29,670 dot txt end parenthesis. 493 00:19:29,670 --> 00:19:32,370 By doing this I have just set all the contents 494 00:19:32,370 --> 00:19:36,060 of test dot txt into the temporary file. 495 00:19:36,060 --> 00:19:38,190 Now if I want to show the contents of that file, 496 00:19:38,190 --> 00:19:41,190 I'll simply use echo dollar sign temp file, 497 00:19:41,190 --> 00:19:43,290 and that'll display the contents of that file 498 00:19:43,290 --> 00:19:46,080 that I just put in that variable to my screen. 499 00:19:46,080 --> 00:19:46,950 Now on the other hand, 500 00:19:46,950 --> 00:19:49,020 if I want to send data to a file, 501 00:19:49,020 --> 00:19:50,820 I can use the greater than symbol 502 00:19:50,820 --> 00:19:52,620 instead of the less than symbol. 503 00:19:52,620 --> 00:19:54,510 Less than means input. 504 00:19:54,510 --> 00:19:56,103 Greater than means output. 505 00:19:56,103 --> 00:19:58,650 Now there's two ways to write to a file. 506 00:19:58,650 --> 00:20:01,740 One is to use the single greater than sign. 507 00:20:01,740 --> 00:20:02,573 When you do this, 508 00:20:02,573 --> 00:20:06,030 any input you give is going to go into that file. 509 00:20:06,030 --> 00:20:08,130 If that file already exists, 510 00:20:08,130 --> 00:20:11,130 it's actually going to be overwritten with what you put there. 511 00:20:11,130 --> 00:20:13,530 Now if you want to append things to that file, 512 00:20:13,530 --> 00:20:15,960 you're going to use a double greater than sign. 513 00:20:15,960 --> 00:20:16,950 So for example, 514 00:20:16,950 --> 00:20:18,840 if I said echo quote 515 00:20:18,840 --> 00:20:21,120 this is now going to be added to the end of the file 516 00:20:21,120 --> 00:20:23,087 as of the next line end quote 517 00:20:23,087 --> 00:20:26,700 greater than greater than test dot txt, 518 00:20:26,700 --> 00:20:28,440 that's exactly what's going to happen. 519 00:20:28,440 --> 00:20:30,810 That string I just typed is going to be echoed 520 00:20:30,810 --> 00:20:32,250 instead of going to the screen, 521 00:20:32,250 --> 00:20:34,980 it's going to go into the file at the end of the file 522 00:20:34,980 --> 00:20:37,560 without overriding the current contents. 523 00:20:37,560 --> 00:20:40,080 All right let's go ahead and take a look at a short script 524 00:20:40,080 --> 00:20:42,990 written in Bash and try to understand what it's doing. 525 00:20:42,990 --> 00:20:46,507 Well the first command we have is if dollar sign one 526 00:20:46,507 --> 00:20:49,080 does not equal empty. 527 00:20:49,080 --> 00:20:50,340 What is that telling us? 528 00:20:50,340 --> 00:20:53,130 It's saying that if there is nothing there, 529 00:20:53,130 --> 00:20:54,480 then don't do anything. 530 00:20:54,480 --> 00:20:56,760 But if it's not empty, 531 00:20:56,760 --> 00:21:00,450 then our target file is going to equal dollar sign one, 532 00:21:00,450 --> 00:21:01,800 that variable. 533 00:21:01,800 --> 00:21:03,780 We're going to set our report directory 534 00:21:03,780 --> 00:21:06,390 to var slash log slash nmap. 535 00:21:06,390 --> 00:21:08,190 So we're probably going to be doing something with nmap 536 00:21:08,190 --> 00:21:10,500 if we're setting it to the nmap directory. 537 00:21:10,500 --> 00:21:14,760 Next for target in dollar sign cat target file. 538 00:21:14,760 --> 00:21:17,511 Now there we can see that for the variable target, 539 00:21:17,511 --> 00:21:20,767 we are going to assign each line inside that target file 540 00:21:20,767 --> 00:21:22,680 to the value of target, 541 00:21:22,680 --> 00:21:24,360 and then run through that loop. 542 00:21:24,360 --> 00:21:25,830 Once we run out of lines, 543 00:21:25,830 --> 00:21:27,870 that would be the end of that for loop, 544 00:21:27,870 --> 00:21:30,150 and we will be finished with doing these commands. 545 00:21:30,150 --> 00:21:32,730 Next we're going to echo scanning target, 546 00:21:32,730 --> 00:21:34,710 whatever that target is that we just pulled in 547 00:21:34,710 --> 00:21:37,860 from that target file. So what do we have on the next line? 548 00:21:37,860 --> 00:21:42,180 Well we have slash user slash bin slash nmap dash ON 549 00:21:42,180 --> 00:21:43,290 and then a lot of stuff, 550 00:21:43,290 --> 00:21:44,123 as you can see, 551 00:21:44,123 --> 00:21:45,477 it takes up over two lines. 552 00:21:45,477 --> 00:21:47,550 Now what is this telling us to do? 553 00:21:47,550 --> 00:21:51,240 Well this is saying we're going to run the nmap command 554 00:21:51,240 --> 00:21:53,220 and we're going to use it with these different parameters. 555 00:21:53,220 --> 00:21:54,677 And then we have the done. 556 00:21:54,677 --> 00:21:58,290 Otherwise we're going to echo you did not provide any command 557 00:21:58,290 --> 00:22:03,290 line options usage program parenthesis file echo echo 558 00:22:03,480 --> 00:22:06,390 and then fi to end the if loop. 559 00:22:06,390 --> 00:22:09,300 So what is this short Bash script really doing for us? 560 00:22:09,300 --> 00:22:11,100 Have you figured it out yet? 561 00:22:11,100 --> 00:22:12,411 Well if not pause the video, 562 00:22:12,411 --> 00:22:13,680 look through it, 563 00:22:13,680 --> 00:22:15,510 and then restart it so you can see 564 00:22:15,510 --> 00:22:17,610 if you got the right answer. 565 00:22:17,610 --> 00:22:18,570 All right you're back? 566 00:22:18,570 --> 00:22:19,403 Great. 567 00:22:19,403 --> 00:22:20,670 So what is this script doing? 568 00:22:20,670 --> 00:22:22,920 Well it's going to take in from the command line 569 00:22:22,920 --> 00:22:25,170 we're going to run it by writing the program name, 570 00:22:25,170 --> 00:22:26,010 the script, 571 00:22:26,010 --> 00:22:28,170 and then giving it a file. 572 00:22:28,170 --> 00:22:30,480 Every time there is something in that file, 573 00:22:30,480 --> 00:22:32,940 like an IP address or a domain name, 574 00:22:32,940 --> 00:22:35,460 it's going to run an nmap scan against it. 575 00:22:35,460 --> 00:22:37,650 So all this command is doing is allowing me 576 00:22:37,650 --> 00:22:40,830 to take whatever inputs from a file, 577 00:22:40,830 --> 00:22:43,200 one per line for IP addresses 578 00:22:43,200 --> 00:22:45,960 and run a different scan on them each time. 579 00:22:45,960 --> 00:22:46,950 So in this case, 580 00:22:46,950 --> 00:22:48,480 I'm going to pull the file in, 581 00:22:48,480 --> 00:22:50,610 I'm going to read one at a time from there, 582 00:22:50,610 --> 00:22:52,110 and every time there's something on the line 583 00:22:52,110 --> 00:22:53,100 and it's not empty, 584 00:22:53,100 --> 00:22:55,020 I'm going to run an nmap scan against it. 585 00:22:55,020 --> 00:22:56,699 Now what is this nmap scan doing? 586 00:22:56,699 --> 00:22:59,580 Well this is a slow comprehensive scan. 587 00:22:59,580 --> 00:23:00,810 We're using T4, 588 00:23:00,810 --> 00:23:02,400 which is not too aggressive. 589 00:23:02,400 --> 00:23:03,480 We're using dash a, 590 00:23:03,480 --> 00:23:04,740 which searches for everything 591 00:23:04,740 --> 00:23:06,960 including OS detection and versioning. 592 00:23:06,960 --> 00:23:09,120 We're doing SS for a sin scan. 593 00:23:09,120 --> 00:23:13,680 We're using a dash ON for output files in nmap format, 594 00:23:13,680 --> 00:23:16,320 and each one is going to be saved to its own file 595 00:23:16,320 --> 00:23:18,240 named target dot nmap. 596 00:23:18,240 --> 00:23:20,580 So if I had three IP addresses, 597 00:23:20,580 --> 00:23:23,190 say I had scanme.nmap.org, 598 00:23:23,190 --> 00:23:27,150 Jason ion.com and Diontraining.com, 599 00:23:27,150 --> 00:23:28,620 it's going to pull each of those. 600 00:23:28,620 --> 00:23:31,950 It's going to do a full nmap scan and save a file, 601 00:23:31,950 --> 00:23:33,891 Jasondion.com dot nmap, 602 00:23:33,891 --> 00:23:36,360 Diontraining.com dot nmap, 603 00:23:36,360 --> 00:23:38,790 right? And I can go back and look at those results later. 604 00:23:38,790 --> 00:23:39,990 So I can run this script, 605 00:23:39,990 --> 00:23:40,823 go home, 606 00:23:40,823 --> 00:23:43,470 come back the next day and have all my scans completed, 607 00:23:43,470 --> 00:23:44,700 it's really great. 608 00:23:44,700 --> 00:23:46,170 And so instead of me having to run the scan 609 00:23:46,170 --> 00:23:48,240 three different times on three different IPS, 610 00:23:48,240 --> 00:23:49,800 I can just give it a file 611 00:23:49,800 --> 00:23:51,600 and the script will pull the information out 612 00:23:51,600 --> 00:23:53,220 and run those scans for me. 613 00:23:53,220 --> 00:23:56,700 So what might a question like this look like on the exam? 614 00:23:56,700 --> 00:23:59,250 Well they might give you something like this and then say, 615 00:23:59,250 --> 00:24:00,690 what's the function of it? 616 00:24:00,690 --> 00:24:02,871 And the correct answer would be that this is performing 617 00:24:02,871 --> 00:24:06,600 an nmap scan against targets provided from an input file, 618 00:24:06,600 --> 00:24:08,040 something like that right? 619 00:24:08,040 --> 00:24:09,030 That's the idea here. 620 00:24:09,030 --> 00:24:11,520 And so you don't need to understand every single nuance 621 00:24:11,520 --> 00:24:12,450 of this script, 622 00:24:12,450 --> 00:24:14,691 but you should be able to identify that it's a Bash script 623 00:24:14,691 --> 00:24:17,370 and what the basic function is. 624 00:24:17,370 --> 00:24:18,300 In this case, 625 00:24:18,300 --> 00:24:20,040 it's going to go through a file, 626 00:24:20,040 --> 00:24:22,170 read each time what's in that file, 627 00:24:22,170 --> 00:24:23,913 and run an nmap scan against them.