2-1 Linux operating system and common commands, 2-1 Linux
Edit it based on the beginner videos 2-1 and 2-2 of Marco's linux
1. GUI and CLI
GUI: Graphic User Interface
CLI: Command Line Interface
Note: In Windows, DLL: Dynamic Link Library is a Library file. In fact, there is a similar SO: Shared Object in Linux.
2. Commands
Format: # command options ...... Arguments .........
Note: Some options include parameters rather than command parameters.
3. ls: list lists the subdirectories and files of the specified file, which are omitted as the current directory.
Note: The file System is a hierarchical management.
Directory: working directory/Current directory
-L: long format, displaying details
-H: human readable for unit conversion. Differences between the following two images
-A: all indicates that all files are displayed.
In Linux, all hidden files start with., that is, hidden files starting with. are displayed.
. Indicates the current directory
.. Indicates the upper level of the current directory
-A: All files are displayed, but not including. And ..
-D: displays the directory attributes.
4. pwd: print working directory shows the current directory path
Note: Linux is/, while Windows is \,
5.-I: Is index node, index node number, first make a knot, there is a blog content http://blog.chinaunix.net/xmlrpc.php? R = blog/article & uid = 28455968 & id = 4105989
The
6.-r: Display in reverse order
7.-R: recursive display
# Ls-R is run in the root directory, and many results are displayed. You can keep this problem first. It should be shown below it and below,
I personally think that this command should not be used frequently, because if a file contains a large number of magnitude, the Operation will consume a lot of resources.
8. cd: change directory
Cd can only be a directory, not a file
Compare ls/etc/issue and cd/etc/issue. Of course, this path is generally not used, but the problem is explained.
Ls is to display the following content, while cd is just to open the directory, not to look at the specific things below.
NOTE: If cd is followed by a slash (/), it indicates to find it from the root directory. If not, it means to find it under the root directory.
Cd returns to the home directory of the user without adding any parameters.
Cd ~ Username: Enter the Home Directory of the specified user. For example, the returned username is root. If the user is switched
Cd-: refers to the switch between the previous directory and the current directory, similar to the rollback, and then the rollback.
9. The command types are divided into built-in commands (shell built-in) and external commands. An external command has an executable file corresponding to the command name in a certain path of the file system.
Type indicates the type of the command, and which indicates where the executable command is.
10. clear: used for Screen Cleaning.
11. printenv: used to display environment variables, but other information can also be displayed.
12. hash, which means that there are many commands executed in Linux. You need to find them in order in the path for each execution. However, you can use it to store all the used commands in the cache, it will be executed soon. The preceding figure shows the number of clicks.
13. Display System Time
# Date
After Windows is shut down, the time will be normal, because there is a network time server (via NTP network time protocol) in Windows, and RTC (real time click) reads the current time at the beginning of Linux.
# Date is the system time
# Clock is the hardware time, or # hwclock
Note: The running time is, but my system time and hardware time are incorrect.
14. How to obtain the command and use help.
Internal COMMAND # help COMMAND, such as # help cd, but # help ls is not internal.
External COMMAND # COMMAND -- help, for example, # ls-help
Common usage, COMMAND manual, # man COMMAND
Man is divided into eight chapters.
1. USER commands
(/Bin,/usr/bin,/usr/local/bin)
2. System Call
Which chapter should be used first? It should be displayed first. If you want to display other chapters, consider this issue.
The format is # whatis COMMAND, which shows which chapters are available. For example, # whatis ls, # whatis read
3. Library call
4. Special files (device files)
There is no content on the disk, but the access portal of the device exists. It is not a real file, so special files are used. For example, # man 4 tty
Note: This tty has several (# whatis tty). If you use a normal command # man tty is the second graph, use TTY (1) in the upper left corner) you can know the type of tty. If you call the fourth one, run the command # man 4 tty, 3.
5. File Format
Configuration File Syntax
6. Games
7. Miscellaneous
Miscellaneous
8. Manage commands
Only the administrator can use it. (/sbin,/usr/sbin,/usr/local/sbin)
15. supplement the system time of date
[]: Enclosed in parentheses, indicating that the content can be omitted.
|: Multiple vertical bars
<>: Angle brackets indicate that the content must be provided.
... : Three vertices indicate that multiple vertices can appear.
{}: Group, no special significance
NAME: command NAME and function description
SYNOPSIS: usage instructions
DESCRIPTION: Detailed DESCRIPTION of the command function.
FILES: configuration file related to this command
EXAMPLES: Example
See also: For more information, SEE
The modification time should have a default time format as follows, so # date-u MMDDhhmm and # date MMDDhhmm should be the same (which is actually incorrect)
-U can see in the help that it is Coordinated Universal Time, UTC, Greenwich Mean Time, but the default format behind it is MMDDhhmm
The running result is as follows:
The Linux date command can be used to display or set the date and time of the system. In terms of display, you can set the format to be displayed. The format is set to a plus sign followed by several tags,
If it does not start with a plus sign, the time is set, and the time format is MMDDhhmm [[CC] YY] [. ss], where MM is the month, DD is the day, hh is the hour, mm is the minute, CC is the first two digits of the Year, YY is the second digit of the Year, ss is the second digit.
·-D datestr: display the time set in datestr (non-system time)
· -- Help: displays auxiliary messages.
·-S datestr: set the system time to the time set in datestr
·-U: display the current Greenwich Mean Time
· -- Version: displays the version number.
Format, # date + % D
Generally, the system time is accurate, and the hardware time needs to be modified by the system.
# Hwclock-w
Hardware time to system time
# Hwclock-s
Also refer to http://www.runoob.com/linux/linux-comm-date.html
16. Small skills
Flip back: space
Forward screen flip: B
Flip One Line Backward: enter
One row forward: k
17. Search
/KEYWORD backward Lookup
? KEYWORD forward lookup
If there are multiple, n is the next, and N is the previous
Q: Exit
18. online manuals/online files, more detailed, are a supplement to man
# Info date
19. The document directory is in this directory
20. Calendar
Cal: calendar. Note that calculator is a calculator.
# Cal
# Cal 2016
# Cal 12 2016
21. There is also an echo function, which is very common.