Linux-text-3

Bash's variable types are mainly: local variables, local variables, environment variables, positional variables, and special variables, where the $ in special variables? This variable is changing at any time, where the saved data is the execution state return value of the command that was just executed

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Execution status return value $? The number means:

0: Successful execution;

1-255: Execution failed

Use the command line expansion feature to complete the following exercises:

(1), create/testdir directory: A_c, A_d, B_c, B_d

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(2), create/tmp/mylinux directory

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(3), what is the metadata information of a file, what does it mean, and how to view it? How to modify timestamp information for a file

Time Stamp management tool for files:

Touch

File: metadata, data

View file Status: Stat

Three time stamps:

Access time: Atime, reading the contents of a file

Modify Time: Modified, Mtime, change file contents (data)

Change time: Changing times, ctime, meta data changes

Touch command:

Touch [OPTION] ... FILE ...

-a:only Atime

-m:only Mtime

-T STAMP:

[[Cc]yy] MMDDHHMM[.SS]

-C: If the file does not exist, it is not created

(4), how to define the alias of a command, how to reference the execution result of another command in the command?

Command Aliases (alias)

Implemented by the alias command:

(1) Alias

Displays all the available command aliases for the current shell process;

(2) Alias Name= ' VALUE '

Defines the alias name, which is equivalent to executing the command value;

Note: Aliases defined on the command line are valid only for the current shell process, and are defined in the configuration file if you want to be permanently valid;

For the current user only: ~/.BASHRC

Valid for all users:/ETC/BASHRC

Note: The new configuration given by the edit configuration will not take effect immediately;

The bash process re-reads the configuration file:

Source/path/to/config_file

. /path/to/config_file

Undo Alias: Unalias

Unalias [-A] name [name ...]

Note: If the alias is the same as the name of the original command, you can use "\command" if you want to execute the original command;

Reference the execution result of another command-pipeline:

COMMAND1 | COMMAND2 | COMMAND3 |

Note: The last command executes in the child shell process of the current shell process;

(5), displays all the files or directories in the/var directory that start with L, end with a lowercase letter, and have at least one digit (can have other characters) in the middle

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(6), display a file or directory that starts with any number in the/etc directory and ends in a non-numeric

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(7), display the/etc directory, start with a non-letter, followed by a letter and any other length of any character file or directory

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(8), in the/testdir directory to create a tfile beginning, followed by the current date and time of the file, the file name is as follows: Tfile-2016-05-27-09-32-22

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(9), copy all the files or directories in the/etc directory to the/testdir/list02 directory that begin with P and do not end with a number

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(10), copy all files or directories ending with. d in/etc directory to the/testdir/list01 directory

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(11), copy all files in the/etc/directory starting with L or M or N and ending with. conf to the/testdir/list03 directory

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Linux-text-3