command usage and some small exercises for Linux files

1. What are the file management commands on Linux, their common use methods and their related display columns;

Cat: Show open files

-N: Number of rows for all outputs

-B: And-similar, but not for blank lines

TAC: In response to connection and printer

Head: Part of the output file

Tail: The last part of the output file

Less: Show headers and tails to flip to view

-N: Number of rows that can be specified

MORE: Show headers and tails to flip to view

Touch: Creating files (creating files is more secure)

-A: Change atime only

-M: Change Mtime only

-C: Do not create empty files

Stat: Displays metadata for a file

Time stamp:

Atime

Mtime

CTime

PWD: Displays information about the directory in which it resides

CD: Switch directories

CP: Copying Files and directories

-A: You can keep links, file attributes,

-D: Keep links when copying

-F: Directly overwrite the existing directory without prompting

-I: Exactly the opposite of-F

-r: Can copy all subdirectories and files under directory

-L: Do not copy files, just generate linked files

Copy files to/testdir/rootdir/to save root permissions and all subdirectories

MV: Change the name of the file

-I: Interactive

-F: Mandatory

RM: Deleting files

-I: Interactive

-F: Force delete

-F: Recursive

RmDir: Delete Empty directory

-P: Subdirectories are deleted and will become empty directories directly deleted

Echo: Echoing

2. Bash's work characteristics the command execution status return value and command line expansion are related to the contents and the presentation of the following columns;

Features of bash: command history

Save 1000 By default

Environment variable: histsize

Usage:

History: View Historical

-C: Clear command history

-D: Delete the specified entry

-A: Writes the current session's command history into the specified file

Features of BASH: Command completion (TAB)

Find commands that start with a user-specified string based on the lookup method of the built-in or external command

TAB key to complete the command two times tab to display the beginning of the specified string command

Features of bash: path completion:

Two Times Tab key

Features of bash: command line expansion

~: User Directory

~: Specify the user's home directory

Features of bash: input, output redirection, and piping

Output redirection:

COMMAND > POSITION: Overwrite output

COMMAND >> POSITION: Append output

Error redirection:

COMMAND 2> POSITION: Overwrite output

COMMAND 2>> POSITION: Append output

Merge redirection:

COMMAND &> POSITION

COMMAND > POSITION 2> &1

REDIRECT Separately

COMMAND > Postiion 2> POSTION2

Enter redirection:

COMMAND < POSITION

3, use the command line to expand the function to complete the exercise;

Create the/tmp/mylinux directory under the

mylinux/

Bin

Boot

Grup

Dev

etc

Rc.d

Init.d

Sysconfig

Network-scripts

Lib

Modules

Lib64

Proc

Sbin

Sys

Tmp

Usr

Local

Bin

Sbin

Var

Lock

Log

Run

Mkdir-pv/testdir/mylinux/{bin,boot/grup,dev,etc/{rc.d/init.d,sysconfig/network-scripts},lib/modules,lib64,proc , Sbin,sys,tmp,usr/loacl/{bin,sbin},var,lock,log,run}

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

Stat: Used to display inode content

Atime

Mtime: Changes in data

CTime: meta-data changes

Touch change files Atime and Mtime

-A: Change atime

-M: Change Mtime

-C: Do not create empty files

Command aliases and command references for bash features:

Alias

Alias Alias=command

When aliases have the same name as the command:

Absolute path

\command

Effective Scope: The alias of the command line definition, which takes effect from the current session;

Unalias [ALIAS]

-A: Undo all aliases

References for bash support:

‘‘

""

": Reference to the execution result of a command

$()

BASH features filename wildcard (globbing):

*: Any character of any length

P*d, pad, PBD, PD

*ab*c

?: Match any single character

[]: matches any single character in the specified range

[ABC], [A-z], [0-9], [0-9a-z]

[^]: matches any single character outside the specified range

[^0-9a-z]

Character Set:

[[: Space:]]: all whitespace characters

[[:p UNCT:]]: All punctuation

[[: Lower:]]: All lowercase letters

[[: Upper:]]: Any size letter

[[:d Igit:]]: Any number, equivalent to 0-9

[[: Alnum:]]: any number or letter

[[: Alpha:]]: Any case letter

5, how to define the alias of a command, how to reference the execution result of another command in the command?

Alias: Aliases for setting directives

Grammar

alias[alias]=[directive name]

# alias Lx=ls

#lx

Root user-defined aliases:

/ETC/BASHRC: Valid for all users

Normal User:

. BASHRC: Valid only for yourself

6. Display all 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) appear in the middle

ls/var/l*[[:d Igit:]]*[[:lower:]]

7. Displays files or directories that start with any number and end with a non-number in the/etc directory

# ls-ld/etc/[0-9]*[^[:d igit:]]

8, display in/etc directory, start with a non-letter, followed by a letter and any other length of any character file or directory

# ls-ld/etc/[^[:upper:]]*[[:upper:]]*

9. In the/tmp directory, create a file that begins with Tfile, followed by the current date and time, with a filename such as: tfile-2016-05-27-09-32-22

# mkdir-pv/tmp/tfile-$ (Date +%f-%h-%m-%s)

10. Copy all the files or directories in the/etc directory to the/tmp/mytest1 directory that begin with P and do not end with a number

# cp/etc/p*[^[:d igit:]]/tmp/mytest1

11. Copy all files or directories ending with. d in/etc directory to the/tmp/mytest2 directory

12. Copy all files in the/etc directory that begin with L or M or N and end with. conf to the/TMP/MYTEST3 directory

Mkdir-p/tmp/mytest3*

Cp/etc/[lmn]*.conf

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command usage and some small exercises for Linux files