1 00:00:00,090 --> 00:00:01,680 Sometimes, you're going to need 2 00:00:01,680 --> 00:00:04,500 further assistance with the syntax and the different options 3 00:00:04,500 --> 00:00:06,960 for a Linux command that you're using in the Shell. 4 00:00:06,960 --> 00:00:09,300 In this video, you're going to learn how to get the help 5 00:00:09,300 --> 00:00:11,190 you need from within the Shell itself, 6 00:00:11,190 --> 00:00:13,620 using something known as a man page. 7 00:00:13,620 --> 00:00:16,140 No matter what your experience, level or role is, 8 00:00:16,140 --> 00:00:18,300 documentation can help users of Linux 9 00:00:18,300 --> 00:00:20,130 perform a wide variety of activities, 10 00:00:20,130 --> 00:00:22,170 and resolve a wide range of issues. 11 00:00:22,170 --> 00:00:24,150 Because there is no official form of Linux 12 00:00:24,150 --> 00:00:26,670 or single authoritative source of documentation, 13 00:00:26,670 --> 00:00:28,380 you're going to find that documentation 14 00:00:28,380 --> 00:00:30,300 is spread across multiple sources, 15 00:00:30,300 --> 00:00:33,270 including manual pages, built-in help commands, 16 00:00:33,270 --> 00:00:36,570 online documentation projects, Usenet news groups, 17 00:00:36,570 --> 00:00:39,300 internet mailing lists, Q&A websites, 18 00:00:39,300 --> 00:00:41,550 forums and social media, as well as books 19 00:00:41,550 --> 00:00:43,410 and other print resources. 20 00:00:43,410 --> 00:00:45,480 Now, the first one and the most important one 21 00:00:45,480 --> 00:00:47,910 for you to look at is the man pages. 22 00:00:47,910 --> 00:00:50,910 The man pages are available on Linux systems by default, 23 00:00:50,910 --> 00:00:53,190 and they contain a complete documentation 24 00:00:53,190 --> 00:00:55,200 that's specific to each Linux command, 25 00:00:55,200 --> 00:00:57,510 and it's going to be displayed using the man command 26 00:00:57,510 --> 00:01:00,420 from within the command line interface or the Shell. 27 00:01:00,420 --> 00:01:01,650 They usually include information 28 00:01:01,650 --> 00:01:03,150 such as the name of the command, 29 00:01:03,150 --> 00:01:05,730 its syntax, a description of its purpose, 30 00:01:05,730 --> 00:01:08,430 the options it supports, examples of common usage 31 00:01:08,430 --> 00:01:11,190 of the command, and a list of related commands. 32 00:01:11,190 --> 00:01:13,680 Man pages are perhaps the most immediate source of help 33 00:01:13,680 --> 00:01:15,510 available to you, because they're right there 34 00:01:15,510 --> 00:01:17,430 at your fingertips whenever you need to learn more 35 00:01:17,430 --> 00:01:20,520 about a command and what it does or how it operates. 36 00:01:20,520 --> 00:01:23,160 But it can be difficult for somebody who's not familiar 37 00:01:23,160 --> 00:01:25,980 with the formatting of a man page to actually read them. 38 00:01:25,980 --> 00:01:27,660 So, let's talk a little bit 39 00:01:27,660 --> 00:01:30,090 about the different parts of a man page. 40 00:01:30,090 --> 00:01:32,370 Now, the first part is the synopsis. 41 00:01:32,370 --> 00:01:34,620 The synopsis is the part of the man page 42 00:01:34,620 --> 00:01:36,600 that provides the syntax of the command, 43 00:01:36,600 --> 00:01:38,760 along with some example use cases. 44 00:01:38,760 --> 00:01:41,760 For example, when you see bold text, this means something 45 00:01:41,760 --> 00:01:45,360 you would type in exactly as shown into the CLI. 46 00:01:45,360 --> 00:01:47,760 Italic text, on the other hand, should be replaced 47 00:01:47,760 --> 00:01:49,140 with the appropriate argument, 48 00:01:49,140 --> 00:01:51,780 and this may be formatted differently on certain systems, 49 00:01:51,780 --> 00:01:54,090 like an underlying text or a colored text, 50 00:01:54,090 --> 00:01:56,370 depending on your Linux distribution. 51 00:01:56,370 --> 00:02:00,060 Next, we have a part that looks like -abc, 52 00:02:00,060 --> 00:02:01,800 and this indicates that all the arguments 53 00:02:01,800 --> 00:02:04,650 within those brackets are going to be optional. 54 00:02:04,650 --> 00:02:07,320 If you see two arguments separated by a pipe, 55 00:02:07,320 --> 00:02:11,009 like -a|-b, this indicates that the arguments 56 00:02:11,009 --> 00:02:13,860 on the other side of the pipe cannot be used together. 57 00:02:13,860 --> 00:02:16,080 This is an "either or" argument pair 58 00:02:16,080 --> 00:02:17,640 that you have to pick between. 59 00:02:17,640 --> 00:02:21,210 If you see any italics text with an ellipsis, like "..." 60 00:02:21,210 --> 00:02:24,480 after it, this indicates that the argument can be repeated, 61 00:02:24,480 --> 00:02:26,970 and you can have multiple sets of arguments. 62 00:02:26,970 --> 00:02:29,610 The man command also supports different options, 63 00:02:29,610 --> 00:02:33,680 such as -a, -D, -f, -h, -k, -K, -t. 64 00:02:42,480 --> 00:02:45,240 If you type -a, you're going to find 65 00:02:45,240 --> 00:02:47,400 all the entries matching your query. 66 00:02:47,400 --> 00:02:50,430 If you type -D, you're going to be displaying 67 00:02:50,430 --> 00:02:52,200 the debugging information. 68 00:02:52,200 --> 00:02:54,990 If you type in -f this will display 69 00:02:54,990 --> 00:02:56,700 a short description of the command, 70 00:02:56,700 --> 00:02:58,590 along with the man pages. 71 00:02:58,590 --> 00:03:01,050 If you use the -h command, 72 00:03:01,050 --> 00:03:02,610 this is going to display help options 73 00:03:02,610 --> 00:03:04,560 for the man command itself. 74 00:03:04,560 --> 00:03:06,600 If you type -k, 75 00:03:06,600 --> 00:03:08,340 you're going to get a list of all the manuals 76 00:03:08,340 --> 00:03:10,920 and pages and sections that contain the keywords, 77 00:03:10,920 --> 00:03:12,720 along with their location. 78 00:03:12,720 --> 00:03:15,450 If you use the -K, you're going to search 79 00:03:15,450 --> 00:03:18,510 for the specified string on all of the pages. 80 00:03:18,510 --> 00:03:22,080 By typing a -t, the man pages will be formatted 81 00:03:22,080 --> 00:03:23,880 so they can be printed out. 82 00:03:23,880 --> 00:03:25,260 As you're probably already seeing, 83 00:03:25,260 --> 00:03:29,130 man pages can become really complicated, but really useful. 84 00:03:29,130 --> 00:03:30,990 When you look at man page sections, 85 00:03:30,990 --> 00:03:33,960 these are going to define what category the command belongs to. 86 00:03:33,960 --> 00:03:36,180 When a command has more than one section listed, 87 00:03:36,180 --> 00:03:38,460 it means the documentation for the same command 88 00:03:38,460 --> 00:03:40,830 is available for more than one source. 89 00:03:40,830 --> 00:03:42,120 These sections are identified 90 00:03:42,120 --> 00:03:44,490 by the number displayed beside the command. 91 00:03:44,490 --> 00:03:47,820 For example, the command fsck is used to check 92 00:03:47,820 --> 00:03:49,860 and repair the Linux file system. 93 00:03:49,860 --> 00:03:52,740 If you search for fsck in the man pages, 94 00:03:52,740 --> 00:03:56,610 you're going to see fsck(8) displayed. 95 00:03:56,610 --> 00:03:58,380 This indicates which of the eight sections 96 00:03:58,380 --> 00:03:59,940 or categories of man pages 97 00:03:59,940 --> 00:04:02,130 this particular command is assigned to. 98 00:04:02,130 --> 00:04:04,440 Section one contains general commands. 99 00:04:04,440 --> 00:04:06,720 Section two contains system calls. 100 00:04:06,720 --> 00:04:09,510 Section three contains C library functions. 101 00:04:09,510 --> 00:04:11,940 Section four contains special files. 102 00:04:11,940 --> 00:04:15,090 Section five contains file formats and conventions. 103 00:04:15,090 --> 00:04:18,000 Section six contains games and screen savers. 104 00:04:18,000 --> 00:04:20,399 Section seven contains miscellaneous. 105 00:04:20,399 --> 00:04:22,440 And lastly, section eight contains system 106 00:04:22,440 --> 00:04:24,660 administration commands and daemons. 107 00:04:24,660 --> 00:04:26,130 There's also going to be special keys 108 00:04:26,130 --> 00:04:27,180 that can be used to navigate 109 00:04:27,180 --> 00:04:29,550 the Linux man pages on your keyboard. 110 00:04:29,550 --> 00:04:30,990 If you use the Home key, 111 00:04:30,990 --> 00:04:33,450 this moves the cursor to beginning of the man page. 112 00:04:33,450 --> 00:04:34,800 And if you press the End key, 113 00:04:34,800 --> 00:04:37,410 it moves you all the way to the end of that man page. 114 00:04:37,410 --> 00:04:39,510 By pressing Page Up or Page Down, 115 00:04:39,510 --> 00:04:42,660 you'll scroll either up one or down one page at a time. 116 00:04:42,660 --> 00:04:44,460 If you press the forward slash key, 117 00:04:44,460 --> 00:04:47,610 this will begin a new search for a term or text string. 118 00:04:47,610 --> 00:04:49,530 If you press the End key, this will move 119 00:04:49,530 --> 00:04:51,780 to the next occurrence of that search term. 120 00:04:51,780 --> 00:04:53,340 And if you press P, it'll move you 121 00:04:53,340 --> 00:04:55,920 to the previous occurrence of that search term. 122 00:04:55,920 --> 00:04:58,170 Finally, when you're done reviewing the man page, 123 00:04:58,170 --> 00:04:59,970 you can press Q to quit, 124 00:04:59,970 --> 00:05:02,610 and then you'll be returned back to the Shell prompt. 125 00:05:02,610 --> 00:05:05,730 As I said, using man pages is really helpful. 126 00:05:05,730 --> 00:05:07,170 I do recommend that you play around 127 00:05:07,170 --> 00:05:09,810 with the man command a little bit on your Cent OS system, 128 00:05:09,810 --> 00:05:12,510 so you get more comfortable using it on a daily basis.