Linux Getting Started Basics command (i)

Linux Getting Started Basics command
Internal command
Resident Memory: brought by the shell and provided by a command

Help: Get a list of all internal commands (only one part is intercepted)

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Enable Command: Execute this command to enable command commands
Enable-n Command: Execute this command to disable command commands
enable-n: View all commands that are disabled (such as)

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External command execution
There is a corresponding executable line file view path under the file system path: Which-a|--skip-alias; Wheris

which Command: View external commands
which-a COMMAND: View all paths
which The difference between command and which--skip-alias command:
Which command can list aliases and paths and which--skip-alias can ignore aliases to show only the path

Whereis Command: You can view all paths to external commands as well as display help documents
Type Command: Specifies whether an internal command or an external command

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For example, those with builtin are internal commands.

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For example, an external command with a file path
External command execution is sequential:

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The external command executes in the above path sequentially
MESG: Execute this command to change Y to N to disable broadcast
Hash: You can view the external command path cached to memory
-L: The details can be displayed, including aliases-p:path aliases: Aliases to Paths-D: Aliases: Delete command aliases-r: Clear cache for all external commands-T: Show alias Path

Alias how to name an order

For example: Alias ' cd/etc/sysconfig/network-scripts/' to cdnet

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Alias ' grep--color=auto ' to grep, execute the command as follows

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Then execute the command grep result can show you want to check the color of the command is red

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Note: centos6.9 does not have grep in the alias (need to alias) and centos7.3/inside.
Unalias: canceling aliases
Because everyone likes different aliases that want to give commands, different users can start their favorite aliases in their home directory < need to be in:. BASHRC alias > (examples are as follows:)
Perform the nano edit command first:

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The result of executing the above command is:

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Then you need to fill in the aliases you want to add (I'm adding the white ones here):

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Then press CTRL+X to force exit input Y agree to note that the alias you added above has not yet taken effect, you need to execute the source. BASHRC or. BASHRC to take effect (as shown)

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A few commands for shutting down the machine:
init 0,halt,poweroff: All can be turned off

This article is from the "12922045" blog, please be sure to keep this source http://12932045.blog.51cto.com/12922045/1930719

Linux Getting Started Basics command (i)