1 00:00:00,570 --> 00:00:01,589 In this lesson, 2 00:00:01,589 --> 00:00:03,960 we're going to discuss how you conduct operations 3 00:00:03,960 --> 00:00:05,700 on different files and directories 4 00:00:05,700 --> 00:00:07,410 within the Linux operating system 5 00:00:07,410 --> 00:00:09,420 using some basic commands. 6 00:00:09,420 --> 00:00:11,670 First, we're going to talk about cat. 7 00:00:11,670 --> 00:00:14,130 Now, cat is short for concatenate. 8 00:00:14,130 --> 00:00:16,079 This can actually display, combine, 9 00:00:16,079 --> 00:00:18,120 or create text files for you. 10 00:00:18,120 --> 00:00:20,730 Cat is most frequently used to display the contents 11 00:00:20,730 --> 00:00:22,380 of small text files. 12 00:00:22,380 --> 00:00:23,370 Now, keep in mind, 13 00:00:23,370 --> 00:00:26,250 cat does not have a screen scrolling capability. 14 00:00:26,250 --> 00:00:28,710 Instead, it's just going to keep going over and over again 15 00:00:28,710 --> 00:00:31,200 until it shows all of the file on the screen 16 00:00:31,200 --> 00:00:34,350 and so things can go way off your screen pretty quickly. 17 00:00:34,350 --> 00:00:36,120 Now there are some options available to use 18 00:00:36,120 --> 00:00:37,350 with the cat command. 19 00:00:37,350 --> 00:00:38,880 If you use dash N, 20 00:00:38,880 --> 00:00:40,650 this will actually show the line numbers 21 00:00:40,650 --> 00:00:42,330 in front of the output. 22 00:00:42,330 --> 00:00:43,890 If you use dash B, 23 00:00:43,890 --> 00:00:45,900 this will be actually used to number the lines, 24 00:00:45,900 --> 00:00:48,090 excluding any blank lines. 25 00:00:48,090 --> 00:00:49,650 If you use dash S, 26 00:00:49,650 --> 00:00:52,980 this will suppress output of any repeated empty lines. 27 00:00:52,980 --> 00:00:55,380 And option dash V is used to display 28 00:00:55,380 --> 00:00:56,850 non-printable characters, 29 00:00:56,850 --> 00:00:59,310 such as visible characters other than tabs, 30 00:00:59,310 --> 00:01:01,650 new lines, and form feeds. 31 00:01:01,650 --> 00:01:03,630 If you use the option dash E, 32 00:01:03,630 --> 00:01:06,270 you're going to actually create a dollar sign character printed 33 00:01:06,270 --> 00:01:08,010 at the end of each line. 34 00:01:08,010 --> 00:01:09,180 And if you use dash T, 35 00:01:09,180 --> 00:01:10,800 it's going to print out the tabs 36 00:01:10,800 --> 00:01:15,660 either as a carrot I or a carrot L if it's a form feed. 37 00:01:15,660 --> 00:01:16,890 To run the cat command, 38 00:01:16,890 --> 00:01:20,580 simply type in cat, the options, and the file name. 39 00:01:20,580 --> 00:01:23,370 Now, the next command we're going to talk about is head. 40 00:01:23,370 --> 00:01:24,720 Head is a command that displays 41 00:01:24,720 --> 00:01:27,480 only the first 10 lines of each file. 42 00:01:27,480 --> 00:01:30,090 Similarly, we have a command known as tail, 43 00:01:30,090 --> 00:01:33,600 and tail will show us the last 10 lines of each file. 44 00:01:33,600 --> 00:01:35,430 These commands are really useful 45 00:01:35,430 --> 00:01:38,640 if you only need to see the beginning or ending of a file. 46 00:01:38,640 --> 00:01:40,380 Now, why might you do this? 47 00:01:40,380 --> 00:01:42,960 Well, let's say you want to check a recent log entry 48 00:01:42,960 --> 00:01:45,570 by viewing the last 10 lines of the log file. 49 00:01:45,570 --> 00:01:48,180 You can simply run the head or tail command 50 00:01:48,180 --> 00:01:51,990 by typing in head or tail, the options, and the file name. 51 00:01:51,990 --> 00:01:54,900 The tail command has two commonly used options. 52 00:01:54,900 --> 00:01:57,120 The first one is dash F. 53 00:01:57,120 --> 00:01:59,730 Dash F will dynamically watch a file 54 00:01:59,730 --> 00:02:02,310 and it'll output will automatically update on the screen 55 00:02:02,310 --> 00:02:04,380 whenever that file changes. 56 00:02:04,380 --> 00:02:06,570 The dash N option will allow us to control 57 00:02:06,570 --> 00:02:08,940 how many lines are actually being displayed. 58 00:02:08,940 --> 00:02:11,009 So if I type in dash N five, 59 00:02:11,009 --> 00:02:12,870 I'll only see the last five lines 60 00:02:12,870 --> 00:02:16,170 of a file instead of the 10 that's used by default. 61 00:02:16,170 --> 00:02:18,930 Now, the dash F option only works in tail, 62 00:02:18,930 --> 00:02:21,480 but the dash N option where you can specify the number 63 00:02:21,480 --> 00:02:25,590 of lines to display, will work in both head and tail. 64 00:02:25,590 --> 00:02:27,450 Now, there's two more commands that I want to talk 65 00:02:27,450 --> 00:02:30,420 about here when it comes to displaying files to your screen 66 00:02:30,420 --> 00:02:33,030 and these are known as less and more. 67 00:02:33,030 --> 00:02:35,220 Both the less and more commands are similar 68 00:02:35,220 --> 00:02:37,680 in a way that they enable you to display the contents 69 00:02:37,680 --> 00:02:41,460 of a file and page through those one screen at a time. 70 00:02:41,460 --> 00:02:43,710 The less command has some additional features 71 00:02:43,710 --> 00:02:44,760 that more doesn't, 72 00:02:44,760 --> 00:02:46,650 but newer versions of more have added 73 00:02:46,650 --> 00:02:49,830 a lot of those features too, making them pretty similar. 74 00:02:49,830 --> 00:02:52,020 While you're free to use either command you want, 75 00:02:52,020 --> 00:02:54,930 the less command is generally used by most people. 76 00:02:54,930 --> 00:02:56,820 You can run the less or more command 77 00:02:56,820 --> 00:02:58,680 by simply typing less or more, 78 00:02:58,680 --> 00:03:00,810 the options, and the file name. 79 00:03:00,810 --> 00:03:03,000 There's also some common less command options 80 00:03:03,000 --> 00:03:04,710 that you might want to be familiar with. 81 00:03:04,710 --> 00:03:06,120 Things like dash E, 82 00:03:06,120 --> 00:03:07,740 which is used to exit the program 83 00:03:07,740 --> 00:03:10,350 the second time it reaches the end of the file. 84 00:03:10,350 --> 00:03:13,380 The dash capital E option will be used to exit the program 85 00:03:13,380 --> 00:03:15,960 the first time it reaches the end of the file. 86 00:03:15,960 --> 00:03:17,730 If you use dash capital I, 87 00:03:17,730 --> 00:03:20,340 it'll ignore case inside of your searches. 88 00:03:20,340 --> 00:03:21,690 And if you use dash N, 89 00:03:21,690 --> 00:03:24,480 it'll suppress any line numbers in the file. 90 00:03:24,480 --> 00:03:26,430 Navigation and less uses many 91 00:03:26,430 --> 00:03:28,410 of the same commands you've seen before. 92 00:03:28,410 --> 00:03:30,690 things like the arrow keys to scroll up one line 93 00:03:30,690 --> 00:03:33,180 at a time or down one line at a time, 94 00:03:33,180 --> 00:03:36,900 or page up or page down to scroll a page at a time. 95 00:03:36,900 --> 00:03:39,090 You can also use the forward slash character to 96 00:03:39,090 --> 00:03:41,430 search a file for a particular text string. 97 00:03:41,430 --> 00:03:43,710 And if you press N or capital N, 98 00:03:43,710 --> 00:03:46,200 you can move to the next or previous instance 99 00:03:46,200 --> 00:03:48,450 of a search string respectively. 100 00:03:48,450 --> 00:03:52,020 When you're done, just press Q to quit the program. 101 00:03:52,020 --> 00:03:55,110 Another command that's really important is the copy command. 102 00:03:55,110 --> 00:03:57,630 The CP command enables you to copy 103 00:03:57,630 --> 00:04:00,690 and then paste a file or directory someplace else. 104 00:04:00,690 --> 00:04:02,880 The initial object, that file or directory, 105 00:04:02,880 --> 00:04:04,200 will be left where it is, 106 00:04:04,200 --> 00:04:06,660 but an exact duplicate of that object, 107 00:04:06,660 --> 00:04:07,980 that file or directory, 108 00:04:07,980 --> 00:04:10,950 will be created at the destination you specify. 109 00:04:10,950 --> 00:04:12,510 When you're copying directories, 110 00:04:12,510 --> 00:04:15,960 you may want to specify the dash capital R option. 111 00:04:15,960 --> 00:04:19,079 This will copy the directory recursively with everything 112 00:04:19,079 --> 00:04:21,000 underneath it going as well. 113 00:04:21,000 --> 00:04:24,660 To run this command, simply type CP, your options, 114 00:04:24,660 --> 00:04:26,940 and the file or directory name that you're going to copy 115 00:04:26,940 --> 00:04:29,940 and the file or directory name you are going to put it to. 116 00:04:29,940 --> 00:04:30,900 For example, 117 00:04:30,900 --> 00:04:34,110 let's say I wanted to copy the my files directory 118 00:04:34,110 --> 00:04:35,550 and put its contents into the 119 00:04:35,550 --> 00:04:38,850 slash OPT slash my files directory. 120 00:04:38,850 --> 00:04:42,630 I would do this by typing CP dash capital R 121 00:04:42,630 --> 00:04:47,630 tilde slash my files slash OPT slash my files. 122 00:04:48,060 --> 00:04:49,260 If you want to move files 123 00:04:49,260 --> 00:04:52,680 or directories to another location instead of copying them, 124 00:04:52,680 --> 00:04:54,840 you can do this using the move command, 125 00:04:54,840 --> 00:04:57,180 which is written as MV. 126 00:04:57,180 --> 00:04:59,430 MV is similar to the copy command, 127 00:04:59,430 --> 00:05:01,920 but it doesn't leave the initial object, 128 00:05:01,920 --> 00:05:04,380 that file or directory, in place. 129 00:05:04,380 --> 00:05:07,710 Instead, move is more like a cut and paste operation 130 00:05:07,710 --> 00:05:10,320 instead of a copy and paste operation. 131 00:05:10,320 --> 00:05:12,300 The bash shell itself does not have 132 00:05:12,300 --> 00:05:14,820 a dedicated rename command, but instead, 133 00:05:14,820 --> 00:05:17,790 we use the move command to do that function. 134 00:05:17,790 --> 00:05:19,830 The act of moving a file or directory and 135 00:05:19,830 --> 00:05:23,160 supplying a new name is essentially the same as renaming 136 00:05:23,160 --> 00:05:24,750 that file or directory. 137 00:05:24,750 --> 00:05:28,290 The proper way to run the move command is to type move, 138 00:05:28,290 --> 00:05:31,110 the options, the filer directory name to move, 139 00:05:31,110 --> 00:05:33,720 and the file or directory name's destination. 140 00:05:33,720 --> 00:05:36,510 For example, let's say I wanted to move something 141 00:05:36,510 --> 00:05:41,510 from tilde slash file one to slash OPT slash file one. 142 00:05:41,670 --> 00:05:45,840 I can do this by typing MV tilde slash file one 143 00:05:45,840 --> 00:05:49,110 slash OPT slash file one. 144 00:05:49,110 --> 00:05:50,970 When you wish to rename a file, 145 00:05:50,970 --> 00:05:54,240 you can do this by simply typing MV, your options, 146 00:05:54,240 --> 00:05:56,400 the old name, and then the new name. 147 00:05:56,400 --> 00:05:59,310 So, if I wanted to change file one to file two, 148 00:05:59,310 --> 00:06:03,180 I can just type MV file one file two 149 00:06:03,180 --> 00:06:06,570 and it will change file one to become file two. 150 00:06:06,570 --> 00:06:08,100 The next command we're going to talk about 151 00:06:08,100 --> 00:06:09,540 is the touch command. 152 00:06:09,540 --> 00:06:11,520 Now, the touch command is used when you need to 153 00:06:11,520 --> 00:06:14,100 test permissions or simply create files that are 154 00:06:14,100 --> 00:06:16,500 going to be processed by some application. 155 00:06:16,500 --> 00:06:17,730 The touch command is available 156 00:06:17,730 --> 00:06:19,950 in most distributions in Linux. 157 00:06:19,950 --> 00:06:22,080 Touch is going to change the time of access 158 00:06:22,080 --> 00:06:25,470 or the modification time of a file to the current time 159 00:06:25,470 --> 00:06:27,900 or you can use it to actually specify 160 00:06:27,900 --> 00:06:30,390 the time inside of an argument. 161 00:06:30,390 --> 00:06:32,760 Touch is also used to create an empty file 162 00:06:32,760 --> 00:06:34,350 with a specified file name, 163 00:06:34,350 --> 00:06:37,140 assuming that that file doesn't already exist. 164 00:06:37,140 --> 00:06:40,380 To do this, we just type touch and the file name. 165 00:06:40,380 --> 00:06:42,330 When you do this, if the file doesn't exist, 166 00:06:42,330 --> 00:06:43,740 a new one will be created. 167 00:06:43,740 --> 00:06:45,030 If one already exists, 168 00:06:45,030 --> 00:06:48,960 it will update its last access time to the current time. 169 00:06:48,960 --> 00:06:51,870 Another command we have is the remove command. 170 00:06:51,870 --> 00:06:54,540 The remove command is written as RM. 171 00:06:54,540 --> 00:06:57,690 The remove command will remove files and directories. 172 00:06:57,690 --> 00:06:59,550 If you want to do this recursively, 173 00:06:59,550 --> 00:07:02,160 you're going to use the dash capital R option 174 00:07:02,160 --> 00:07:04,980 and this will recursively remove files, sub directories, 175 00:07:04,980 --> 00:07:07,050 and the parent directory itself. 176 00:07:07,050 --> 00:07:09,570 The proper way to run the remove command is to type 177 00:07:09,570 --> 00:07:12,930 remove, the options, and the file or directory name. 178 00:07:12,930 --> 00:07:14,730 So let's say I wanted to remove the 179 00:07:14,730 --> 00:07:18,840 tilde slash my files directory and all of its contents. 180 00:07:18,840 --> 00:07:22,290 I can do that by typing RM dash capital R 181 00:07:22,290 --> 00:07:24,600 tilde slash my files. 182 00:07:24,600 --> 00:07:26,010 There's also going to be times when you 183 00:07:26,010 --> 00:07:28,590 need to remove files but not directories 184 00:07:28,590 --> 00:07:31,380 and you can do this using the unlink command. 185 00:07:31,380 --> 00:07:32,880 When you use the unlink command, 186 00:07:32,880 --> 00:07:35,640 it's very similar to using the remove command. 187 00:07:35,640 --> 00:07:36,810 Now, at this point, 188 00:07:36,810 --> 00:07:38,460 you have seen much of the power 189 00:07:38,460 --> 00:07:40,950 of the LS or list command that we've done to 190 00:07:40,950 --> 00:07:42,630 list the contents of directories 191 00:07:42,630 --> 00:07:44,340 as well as their permissions information 192 00:07:44,340 --> 00:07:47,490 of directories and files when we talked about users, groups, 193 00:07:47,490 --> 00:07:49,440 and permissions earlier in the course. 194 00:07:49,440 --> 00:07:51,150 Now, there are a lot of useful options 195 00:07:51,150 --> 00:07:52,920 when you're using the LS command. 196 00:07:52,920 --> 00:07:55,410 Let's cover a few of these key options. 197 00:07:55,410 --> 00:07:57,690 The first one is dash L. 198 00:07:57,690 --> 00:08:00,960 If you use dash L, this is going to display a long list, 199 00:08:00,960 --> 00:08:03,690 including the permissions, the number of hard links, 200 00:08:03,690 --> 00:08:07,140 the owner, the groups, the size, the date, 201 00:08:07,140 --> 00:08:10,440 and the file name all for you right there on the screen. 202 00:08:10,440 --> 00:08:12,210 If you use dash F, 203 00:08:12,210 --> 00:08:14,790 this is going to be used to display the nature of a file, 204 00:08:14,790 --> 00:08:17,490 basically telling you is it an executable file 205 00:08:17,490 --> 00:08:20,520 and slash if it's going to be a directory. 206 00:08:20,520 --> 00:08:22,440 If you have the dash A option, 207 00:08:22,440 --> 00:08:24,150 this is going to display all the files 208 00:08:24,150 --> 00:08:25,680 in the present directory, 209 00:08:25,680 --> 00:08:28,350 including the files whose names begin with a period, 210 00:08:28,350 --> 00:08:30,240 which is a hidden file. 211 00:08:30,240 --> 00:08:32,460 If you use the dash capital R option, 212 00:08:32,460 --> 00:08:34,890 this'll recursively display all the sub directories 213 00:08:34,890 --> 00:08:37,080 as well as the present directory. 214 00:08:37,080 --> 00:08:38,549 If you use dash D, 215 00:08:38,549 --> 00:08:39,809 it'll display information 216 00:08:39,809 --> 00:08:41,909 about symbolic links or directories 217 00:08:41,909 --> 00:08:43,289 rather than the link's target 218 00:08:43,289 --> 00:08:45,480 or the contents of that directory. 219 00:08:45,480 --> 00:08:47,700 And if you use the dash capital L, 220 00:08:47,700 --> 00:08:50,010 it'll display all the files in the directory, 221 00:08:50,010 --> 00:08:52,170 including your symbolic links. 222 00:08:52,170 --> 00:08:53,670 To run the LS command, 223 00:08:53,670 --> 00:08:57,600 you'll type LS, the options, and the file or directory name. 224 00:08:57,600 --> 00:09:00,270 Normally, when I execute the LS command, 225 00:09:00,270 --> 00:09:03,450 I like to use LS dash LA. 226 00:09:03,450 --> 00:09:04,500 By doing that, 227 00:09:04,500 --> 00:09:07,290 I'm going to list out all the files and directories, 228 00:09:07,290 --> 00:09:08,790 including their permissions, 229 00:09:08,790 --> 00:09:11,130 and the A tells me to show me everything 230 00:09:11,130 --> 00:09:13,380 including those hidden files. 231 00:09:13,380 --> 00:09:14,760 If you're in the bash shell 232 00:09:14,760 --> 00:09:16,650 and you execute the LS command, 233 00:09:16,650 --> 00:09:18,690 you may notice that the results sometimes appear 234 00:09:18,690 --> 00:09:20,280 in different colors. 235 00:09:20,280 --> 00:09:21,900 These colors are used to distinguish the 236 00:09:21,900 --> 00:09:23,400 different file types. 237 00:09:23,400 --> 00:09:26,160 The different colors distinguish normal text files. 238 00:09:26,160 --> 00:09:28,470 while blue is going to be used for directories. 239 00:09:28,470 --> 00:09:32,190 Sky blue will be used for symbolic links and audio files. 240 00:09:32,190 --> 00:09:35,460 And if you're using green, that shows an executable file. 241 00:09:35,460 --> 00:09:38,760 If you have yellow with a black background, that's a device. 242 00:09:38,760 --> 00:09:40,920 If you have pink, that's an image file. 243 00:09:40,920 --> 00:09:42,927 If you have red, that's an archive file. 244 00:09:42,927 --> 00:09:45,270 And if you have red with a black background, 245 00:09:45,270 --> 00:09:47,910 that distinguishes it as a broken link. 246 00:09:47,910 --> 00:09:50,070 These colors can be very useful when you're looking 247 00:09:50,070 --> 00:09:53,010 at this to figure out exactly what you're looking at. 248 00:09:53,010 --> 00:09:54,570 Now, another command we need to talk about 249 00:09:54,570 --> 00:09:56,280 is how we make directories, 250 00:09:56,280 --> 00:09:59,610 and this is going to be done using the MKDIR command. 251 00:09:59,610 --> 00:10:01,500 This is the make directory command. 252 00:10:01,500 --> 00:10:04,110 It's used to create or make a directory. 253 00:10:04,110 --> 00:10:06,150 To use it, you're simply going to give the name 254 00:10:06,150 --> 00:10:08,400 of the directory you want as an argument. 255 00:10:08,400 --> 00:10:13,380 So, I would type MKDIR Jason to create the Jason directory. 256 00:10:13,380 --> 00:10:15,210 If I want to remove that directory, 257 00:10:15,210 --> 00:10:19,590 I can use the remove directory command, which is RMDIR. 258 00:10:19,590 --> 00:10:21,870 Now, when you're using RMDIR, 259 00:10:21,870 --> 00:10:25,800 it will only delete a directory if that directory is empty. 260 00:10:25,800 --> 00:10:27,840 If you want to delete a directory that has things 261 00:10:27,840 --> 00:10:29,940 in it like files or other directories, 262 00:10:29,940 --> 00:10:32,130 you're going to have to use the remove command, 263 00:10:32,130 --> 00:10:34,020 RM with the recursion. 264 00:10:34,020 --> 00:10:38,250 So it's RM dash R and the name of the directory. 265 00:10:38,250 --> 00:10:40,860 To use either make directory or remove directory, 266 00:10:40,860 --> 00:10:43,560 simply type in make directory and the directory name 267 00:10:43,560 --> 00:10:46,020 or remove directory and the directory name. 268 00:10:46,020 --> 00:10:47,040 So, as you can see, 269 00:10:47,040 --> 00:10:48,510 there are lots of different commands 270 00:10:48,510 --> 00:10:50,040 that you need to be familiar with 271 00:10:50,040 --> 00:10:52,200 inside the Linux operating system to get 272 00:10:52,200 --> 00:10:53,880 around in the command line. 273 00:10:53,880 --> 00:10:55,800 I recommend you take some time to practice 274 00:10:55,800 --> 00:10:56,850 each of the ones we covered 275 00:10:56,850 --> 00:10:59,013 in this lesson and get familiar with them.