Linux Basics--shell Command type and command use Help

Joined the caravan for some time, see the group inside the big head to check the blog, only to realize that I have not written homework. As the saying goes, the time is to kill the Pig knife!!! Cough, actually want to say, horse brother Video is long, content thief, for writing is not good to me, write homework pressure mountain, there are wood. Well, well, long story short, get to the point.

Two weeks past, the course progress is a bit behind, this post mainly records the basic command course knowledge, used to comb the knowledge points and deepen the impression, for the future of the road to build a solid foundation of Linux good start, complete the blog and review the relevant knowledge points, hope to accelerate learning pace, slow, keep up with progress, good Good Study,day Day up!

1. Shell command type:

There are two types of shell commands:

1.1 Built-in command: The shell program itself comes with commands that are part of the shell program;

1.2 External command: There is an executable file corresponding to it in a directory

To differentiate between command types, you can use the following command:

# type command/        * To view the types of commands */  

# which Command/        * View the path where the executable file is located * /

For example:

A. Red line identification result tip: "CD" is a shell built-in command.

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B. Red line identification results tip: The executable file for the command is not found in PATH, $PATH: determines which directories the shell will look for commands or programs.

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C. Red line identification results hint: The executable program of the "Man" command is located at the path, stating "Man" is an external command.

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D. The red line indicates the result: "LS" is an individual name, then use the "which" command, you can know the "LS" command its executable file path.

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2. Order Help related

2.1 To get command help information, use the following command:

# Help Command/* Only available for use with internal commands */

# Help CD/        * Get instructions for using the internal command "CD" * /

# Man Command/* View the command manual, "man" Full Name "manual", you can use "Whatis command" to obtain the description of the instructions in the chapter information and introduction * *

# Whatis CP/           * command "CP", corresponding help information in the section */

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# man 1p CP/           * Get the Command "CD" in chapter "1p" Information */

# command–help/* Get command Brief use help */

ls --help/        * get a brief use of the command "LS" help * /

2.2 Linux, the "Man" manual, for different commands or configurations of the manual is located in different chapters, the relevant class can be found in the chapter information in the following table:

1. User commands;

2. System call;

3. Library calls;

4. Special documents, equipment files;

5. file format, i.e. configuration file;

6. Games;

7. Miscellaneous;

8. Management class commands;