4 Big Open source protocol and Linux Basic Command meeting point

Gpl,lgpl,bsd, Apache, the GPL as the GNU General Public License, as long as in a software to use the GPL agreement products, the product must use the GPL agreement, also must open source and free, with so-called "contagious." Both the GPL and the LSPL protect the intellectual property of the original author, avoiding the use of open source code to replicate the development of similar products, is not suitable for it as a basis for the development of two commercial software, but LGPL as the GPL is mainly used for the class library of open-source protocol, it allows commercial software as a class library reference and publish sales.

BSD, as the preferred agreement for corporate companies, requires that the products it uses contain a copyright notice and disclaimer and that it is prohibited to do marketing in the name of the developer, whereas Apache requires a copyright notice and disclaimer for the source user, as well as an agreement on the original code and a patent license statement. But both meet commercial software as or commercial software release sales and encourage code reuse.

Common command line interface has bash,zsh,fish three kinds, the most common is the Bash command interface, for all distributions, you can use the Echo $SHELL to view the current shell type, Linux, the SSH protocol can be used to remotely connect the current system with Xshell. Before we make sure that the system firewall is turned off by SS-TNL command to see if the system is listening on port 22 of the TCP protocol and then viewing the IP address of the system remotely via the Ifconfig or IP Addr List command.

Linux has an important philosophical thinking: All documents, its file system is an inverted tree structure, using hierarchical structure, index for distributed storage, the path of the file is divided into absolute path and relative path two, the file name is strictly case-sensitive, support for any character except/or other names, The maximum length cannot exceed 255 characters, and two files cannot have the same name under the same path. You can view the command type by type,

We can view the current terminal equipment through TTY, ①HELP get the use of internal command help, ②--help used to get External command of the brief use of Help, manual man is stored in the system/usr/share/man location, man's chapter is divided into 1: User command ; 2: System call; 3:c library call; 4: Device files and special files; 5: file format; (profile format) 6: Game use Help; 7: Miscellaneous; 8: Management tools and daemons; 9: Kernel history, etc. whatis used to see the chapters under which the keywords have manuals, But not every keyword in man has a handbook under all chapters; Makewhatis is used to execute a query database to manually update the database, man less gets the use Help, man-m is used to find the relevant keyword handbook and display it under the specified path; ③info online documentation for commands ; ④ view the application's own Help document; ⑤ the document on the master station of the reference program; ⑥ View the system release claims document; ⑦; search by searching engine; All search results are cached in the hash table;

Bash has three features: ① command alias: You can use alias to get the current user under the command, alias Name= "definition alias, unalias name revocation alias; ② command history: Histsize and Histfilesize The total number of bars by default is 1000 The current user's command history file is placed in the ~/.bash_history, history is used to perform command history operations, you can change the historical record by Histcontrol the environment variable value, histcontrol= Ignoredups is used to ignore consecutive and identical duplicate commands, ignorespace means that the command that starts with a white space character is not recorded in the history command, Ignoreboth means both are in effect, ③ shortcut CTRL + A (to the beginning of the line), +e (at the end of the row); K ( Delete the contents of the cursor at the end of the line), U (delete the beginning of the line to the cursor where the content);

Which is used to display the full path of the command,-a displays all matching program files instead of the first,--skip-alias indicates a skip alias, Whereis represents this command binary, source code, user manual location,-B (equivalent to which),-M (only show manual) Who is used to see who is logged on to the current system,-R (Display runlevel),-B (the time the system starts), W indicates who is logged in and what is being done, WhoAmI displays my account, and Poweroff,halt shuts down the system, reboot reboots the system.

4 Big Open source protocol and Linux Basic Command meeting point