1, df command
Role: View disk space.
Syntax: # df--h
2, free instruction
Role: View (available) memory.
Syntax: #Free -m (expressed in units of view has been mb)
Swap: a temporary memory when the system is not enough real memory can be temporary disk space to act as memory.
3, head instruction
Role: view a file before n rows, if n is not specified, the default is 10 lines before.
Syntax: #head -n file path [n represents a number]
4, tail command
Role 1: the end of the line n view a file, if n is not specified, the default display after line 10
Syntax: # tail -n file path (n represents a number)
Role 2: You can view the dynamic changes in a document by the tail command.
Syntax: # tail -f file path
5, less instruction
Action: See file content with a small output, press the auxiliary function key (number, enter, space key, down arrow keys) for more
Syntax: file path #less need to see
6, wc command
Role: statistics file content information
Syntax: #wc -lwc need statistics file path
-l indicates the number of rows
-w represent words, the number of words in accordance with spaces to determine the number of words
-c represents bytes, the number of bytes.
7, date instructions (emphasis)
Action: indicates the operation time and date (read, set)
Syntax 1: #date output in the form of: March 23, 2018 Friday 13:23:23
Syntax 2: #date + F.% (Equivalent to #date "+% Y-% m-% d") output form: 2018-02-23
Syntax. 3: #date: "% T + F." (Equivalent to #date "+ Y-% m-% d % H:% M:% S") quotation marks so that "date and hour, minute" has become a indivisible whole.
Output form: 2018-03-23 13:29:22
Acquisition time before or after the (backup)
Syntax. 4: #date -d "-1 day" "+ Y-M-% D%% H:% M:% S" (symbol + indicates (after) - represented (before), the unit represented day day, month represents month, year is the year)
8, cal instruction
Role: to operate Calendar
Syntax. 1: #cal equivalent to #cal -1 (a direct output current month)
Syntax 2: #cal -3 (expressed on a month + current month + output next month calendar)
Syntax 3: #cal -y year (represents the output of a calendar year)
9, clear / ctrl + L instruction
Action: remove the terminal already exist in the command and the result (information).
Syntax: #clear or shortcut keys: Ctrl + L
The idea is needed: the command is not really clear information before, but to hide the information before the top, you can continue to view the previous information by a scroll bar.
10, pipes (important)
Fu pipe: L (delimiter is not lowercase l)
Action: duct may be generally used for "filtering", "Special", "expansion processing."
Syntax: pipes can not be used alone, with some of the instructions must be stated before use with, its main function is to assist role.
Filter Case: need to check out the piping document name contains "y" when the letter of the root directory.
[root@localhost ~]#ls /l grep y
Reference: programmers dark horse liunx from entry to the master
