Mathematical method of thinking-the basic technology of Distributed Computing-linux/unix (3)

Clip:

~ Represents the current user's home folder

. It represents the current folder

.. It represents the parent folder

Link file

Using a different file name refers to the same data or program. Hard Links

In the same physical file system, create a hard link

-bash-4.2$ Find ~-name "*.py" >mypylist

Ls-la indicates that all files under the current folder, including hidden files, are viewed in a long format, with the following meanings for each field:

Each of the 7 segments is:

2. File properties: Drwxr-xr-x
4. Number of file hard links or folder folders: 3 (the field for an empty folder is 2.) Indicates that there are two subfolders under the folder. Because each folder has a subfolder that points to itself "." and a subfolder that points to its parent folder "..." ）
6. All Users: User
8. Owning user group: group
10. File size: 102 byte
12. Modification Time: Mar11 22:56
14. File name: filename

-bash-4.2$ Ls-la
Total dosage 151228
DRWX------. 6 MYHASPL myhaspl 4096 September 18 08:55.
Drwxr-xr-x. 3 root root 20 September 10 08:23..
-RW-------. 1 myhaspl myhaspl 1915 September 18:05 bash_history
Drwxr-xr-x. 9 MYHASPL myhaspl 4096 June 14:38 hadoop-2.4.1
-rw-r--r--. 1 myhaspl myhaspl 15417097 June 14:42 hadoop-2.4.1-src.tar.gz
-rw-r--r--. 1 myhaspl myhaspl 138656756 June 14:42 hadoop-2.4.1.tar.gz
-rw-r--r--. 1 myhaspl myhaspl 1454 September 10:53 mydoclist
-rw-rw-r--. 1 MYHASPL MYHASPL 88 September 17:25 MyList
-rw-rw-r--. 1 myhaspl myhaspl 357304 September 08:55 mypylist
-rw-rw-r--. 1 myhaspl myhaspl 31954 September 18:02 Myse
Drwxr-xr-x. 8 MYHASPL myhaspl 4096 September 10:39 numpy
DRWXR-----. 3 MYHASPL myhaspl 18 September 16:21. PKI
Drwxrwxr-x. Root root 4096 September 16:25 pypy-2.3.1-src
-rw-rw-r--. 1 myhaspl myhaspl 357304 September 17:57 SE
-bash-4.2$ LN mypylist mypylist1
-bash-4.2$ Ls-la
Total dosage 151580
DRWX------. 6 MYHASPL myhaspl 4096 September 18 08:56.
Drwxr-xr-x. 3 root root 20 September 10 08:23..
-RW-------. 1 myhaspl myhaspl 1915 September 18:05 bash_history
Drwxr-xr-x. 9 MYHASPL myhaspl 4096 June 14:38 hadoop-2.4.1
-rw-r--r--. 1 myhaspl myhaspl 15417097 June 14:42 hadoop-2.4.1-src.tar.gz
-rw-r--r--. 1 myhaspl myhaspl 138656756 June 14:42 hadoop-2.4.1.tar.gz
-rw-r--r--. 1 myhaspl myhaspl 1454 September 10:53 mydoclist
-rw-rw-r--. 1 MYHASPL MYHASPL 88 September 17:25 MyList
-rw-rw-r--. 2 myhaspl myhaspl 357304 September 08:55 mypylist
-rw-rw-r--. 2 myhaspl myhaspl 357304 September 08:55 mypylist1
-rw-rw-r--. 1 myhaspl myhaspl 31954 September 18:02 Myse
Drwxr-xr-x. 8 MYHASPL myhaspl 4096 September 10:39 numpy
DRWXR-----. 3 MYHASPL myhaspl 18 September 16:21. PKI
Drwxrwxr-x. Root root 4096 September 16:25 pypy-2.3.1-src
-rw-rw-r--. 1 myhaspl myhaspl 357304 September 17:57 SE
-bash-4.2$ LN mypylist mypylist2
-bash-4.2$ Ls-la
Total dosage 151932
DRWX------. 6 MYHASPL myhaspl 4096 September 18 09:27.
Drwxr-xr-x. 3 root root 20 September 10 08:23..
-RW-------. 1 myhaspl myhaspl 1915 September 18:05 bash_history
Drwxr-xr-x. 9 MYHASPL myhaspl 4096 June 14:38 hadoop-2.4.1
-rw-r--r--. 1 myhaspl myhaspl 15417097 June 14:42 hadoop-2.4.1-src.tar.gz
-rw-r--r--. 1 myhaspl myhaspl 138656756 June 14:42 hadoop-2.4.1.tar.gz
-rw-r--r--. 1 myhaspl myhaspl 1454 September 10:53 mydoclist
-rw-rw-r--. 1 MYHASPL MYHASPL 88 September 17:25 MyList
-rw-rw-r--. 3 MYHASPL myhaspl 357304 September 08:55 mypylist
-rw-rw-r--. 3 MYHASPL myhaspl 357304 September 08:55 mypylist1
-rw-rw-r--. 3 MYHASPL myhaspl 357304 September 08:55 mypylist2
-rw-rw-r--. 1 myhaspl myhaspl 31954 September 18:02 Myse
Drwxr-xr-x. 8 MYHASPL myhaspl 4096 September 10:39 numpy
DRWXR-----. 3 MYHASPL myhaspl 18 September 16:21. PKI
Drwxrwxr-x. Root root 4096 September 16:25 pypy-2.3.1-src
-rw-rw-r--. 1 myhaspl myhaspl 357304 September 17:57 SE

You can see the number of hard links in Mypylist added

the whole content of this blog is original. If reproduced please indicate the sourcehttp://blog.csdn.net/myhaspl/

Create soft links that can span different physical file systems, also known as Symbolic link files. Unlike hard links, it is a separate file. The path name that holds the destination file.

-bash-4.2$ ln-s mypylist mypylists
-bash-4.2$ Ls-la
Total dosage 151932
DRWX------. 6 MYHASPL myhaspl 4096 September 18 09:35.
Drwxr-xr-x. 3 root root 20 September 10 08:23..
-RW-------. 1 myhaspl myhaspl 1915 September 18:05 bash_history
Drwxr-xr-x. 9 MYHASPL myhaspl 4096 June 14:38 hadoop-2.4.1
-rw-r--r--. 1 myhaspl myhaspl 15417097 June 14:42 hadoop-2.4.1-src.tar.gz
-rw-r--r--. 1 myhaspl myhaspl 138656756 June 14:42 hadoop-2.4.1.tar.gz
-rw-r--r--. 1 myhaspl myhaspl 1454 September 10:53 mydoclist
-rw-rw-r--. 1 MYHASPL MYHASPL 88 September 17:25 MyList
-rw-rw-r--. 3 MYHASPL myhaspl 357304 September 08:55 mypylist
-rw-rw-r--. 3 MYHASPL myhaspl 357304 September 08:55 mypylist1
-rw-rw-r--. 3 MYHASPL myhaspl 357304 September 08:55 mypylist2
lrwxrwxrwx. 1 MYHASPL myhaspl 8 September 09:35 mypylists-mypylist

I/O redirection, the file Description descriptor for standard input (stdin) is 0. Standard output (STDOUT) has a file descriptive descriptor of 1, and a standard error output (stderr) with a file descriptor of 2

Standard output redirection: 1>filename or 1>>filename

-bash-4.2$ echo "AAA" 1> ABC
-bash-4.2$ Cat ABC
Aaa

-bash-4.2$ echo "AAA" 1>> ABC
-bash-4.2$ Cat ABC
Aaa
Aaa
-bash-4.2$

Standard error Output redirect: 2>filename or 2>>filename

-bash-4.2$ rm/root/* 2>error.log

-bash-4.2$ Cat Error.log
RM: Unable to delete "/root/*": Insufficient permissions
-bash-4.2$

The i>&j indicates that the output file represented by the file description descriptor I is redirected to the file described by the file descriptor J.

For general files:

r = Agree to read the contents of the file

w = Agree to change the contents of the file

x = consent to run the file

For folders:

r = agree to list files and subfolders under this folder

w = consent to generate and delete files under this folder

x = consent to access the folder

U on behalf of all (user) G on behalf of all the groups (group) O on behalf of others. But not u and G (other) a represent the whole person. which includes U,g and O.

chmod ability to change permissions

chmod [User Type] (+/-) access to the format file or folder name

Example:

chmod a+w MyText

Set the mytext to all people writable.

-bash-4.2$ echo "Ls;echo \" Ok\ "" >myrun
-bash-4.2$ Cat Myrun
Ls;echo "OK"
-bash-4.2$ chmod +x./myrun
-bash-4.2$./myrun
ABC hadoop-2.4.1 mydoclist mypylist1 myrun pypy-2.3.1-src
Abd hadoop-2.4.1-src.tar.gz mylist mypylist2 myse SE
Error.log hadoop-2.4.1.tar.gz mypylist mypylists numpy

Ok

Pagination Display file

-bash-4.2$ more Mypylist
/home/myhaspl/pypy-2.3.1-src/pytest.py
/home/myhaspl/pypy-2.3.1-src/dotviewer/graphparse.py
/home/myhaspl/pypy-2.3.1-src/dotviewer/__init__.py
/home/myhaspl/pypy-2.3.1-src/dotviewer/graphclient.py
/home/myhaspl/pypy-2.3.1-src/dotviewer/msgstruct.py
/home/myhaspl/pypy-2.3.1-src/dotviewer/graphpage.py
/home/myhaspl/pypy-2.3.1-src/dotviewer/graphserver.py
/home/myhaspl/pypy-2.3.1-src/dotviewer/dotviewer.py

.............

............

Copy files

-bash-4.2$ CP mypylist MYL1

Move files (You can also change the file name)

-bash-4.2$ MV Myl1 MYL2

Renamed

-bash-4.2$ ls
ABC hadoop-2.4.1 mydoclist mypylist mypylists numpy
Abd hadoop-2.4.1-src.tar.gz myl2 Mypylist1 myrun pypy-2.3.1-src
Error.log hadoop-2.4.1.tar.gz mylist mypylist2 myse SE
-bash-4.2$ Rename list lst *pylist*
-bash-4.2$ ls
ABC hadoop-2.4.1 mydoclist mypylst mypylsts numpy
Abd hadoop-2.4.1-src.tar.gz myl2 Mypylst1 myrun pypy-2.3.1-src
Error.log hadoop-2.4.1.tar.gz mylist mypylst2 myse SE
-bash-4.2$

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Mathematical method of thinking-the basic technology of Distributed Computing-linux/unix (3)