Second Lecture: The second lesson Linux operating system and common commands
1.date-Display System time
Modification time
2.liunx time mode: Crystal oscillator, high-level error of one second per million. On the host is the crystal oscillator time. Crystal oscillator to power the line, the motherboard has a button battery. The time on the motherboard is called Rtc,real clock
NTP (Network time): PROTOCL
Linux: When the system starts to read the RTC (Hardware clock), after the read success is not in use RTC time, the system kernel itself simulates the oscillator in the system internal simulation time, establishes the system clock through the software method.
Date Display system time
Clock Display hardware time
Hwclock Display Hardware Time
3. How to get command use Help
Internal command: Help command, such as Help Cd,help ls
External command: Use long Select command--help, such as Whichis--help
Command Manual (internal and External command common): Man command, such as: Man Ls,man
Man internal command: Opens the shell to which the command belongs
Man external command: Open the command one using the document
How do I see the man chapter? Whatis command
Whatis command shows which chapters of the man the commands appear in
Man is divided into chapters, and the common chapters are 8 chapters. Command layout in the first chapter of man, the default is to display the chapter, if the man is a section of the chapter will show that this command appears.
LS (1): User command, all users can use the command, including ordinary users (/bin,/usr/bin/,/usr/local/bin)
LS (2): System call [export lang=en solve garbled, man 2 LS display chapter II]
LS (3): Show Library Call
LS (4): Special file (device file)
LS (5): File format: a command corresponding to the format of the configuration file, passwd, the syntax of the configuration file
LS (6): Games Game Description
LS (7): Miscellaneous (Miscellaneous), inconvenient to categorize.
LS (8): Administrative Command (/sbin,/usr/sbin/,/usr/local/sbin)
4. Command Format learning
Date [OPTIONS] [-u|-c|-d] "[] means you can omit" "<> indicate what must be given" "| Indicates multiple selection one use "" ... Indicates that multiple "{} groupings" can occur
5.MAN Format Description
Name: command name, Function brief description
Synopsis: Usage notes, including available options
DESCRIPTION: Detailed description of the command function, including the meaning of each option
Options: Fine-grained description of the meaning of each option
Files: The configuration file associated with this command
BUGS:
EXAMPLES: Examples of Use
See ALSO: Another reference
Man use command:
Turn One screen: SPACE
Front Turn One screen: b
One line after the turn: ENTER
Front Turn line: K
Search function:/keyword+enter backward Search
? Keyword+enter Forward Search
40 minutes
Second Lecture: The second lesson Linux operating system and common commands
