"Linux file View, operation"

First, how the shell handles commands

• 1.shell divides the command into multiple parts based on the space characters that appear in the command
• 2. Determine whether the first field is an internal command or an external command

Internal command: Command path built into the shell (shell builtin) external command: The command paths installed by installing another application or service: The hierarchical relative path of the directory that is necessary to find or locate a file: The path to find from the working directory. Current working directory: The parent directory of the parent directory root of the current working directory is also the root absolute path: The path variable to look up from the root (/): Memory space variable value: null variable for data stored in memory space: Empty environment variable Path (path), absolute path: path=path1:path2:path3: ...

• 3. Determine whether the other field is an option or a parameter, correctly judged, if it is executed correctly, and returns an error message if the error
• 4. Press ENTER during command writing to submit the written content to the shell for execution
• 5. If you want to cancel the command before submitting the shell, use CTRL + C

Second, file view, operation

Help class
Man,help,info,whereis,which,whatis
Directory Operation class
Ls,pwd,cd,mkdir,rmdir
File Operation class
Nano,touch,rm,cp,mv,stat
File View class
Cat,tac,head,tail,less,more
Text Processing
Cut,sort,uniq,tr,sed,awk

1. View

• Ls-->list

The list displays the contents of the Directory usage:ls[OPTION] ... [FILE] ... []: Optional Content {}: Required content|: Selecting a default parameter is the working directory option:-L: Long format output-RW-------.1Root root1211May One  .:Genevaanaconda-ks.cfg The first bit indicates the type of file:-: Denotes normal file (f,fileB: Indicates block device file (block) C: Character device file (charact) d: Directory file L: Symlink file (symbol link) P: Pipe file (pipe) s: Socket file (socket) second to tenth bit: file's permission bit, three sets of permission bits , each group includes three permission characters, rwx, read and write execution. If you don't have permission, use-instead of the second paragraph, number 1: Indicates the number of times the file has been hard-linked third paragraph: The owner of the file, root fourth: The file see the group, root fifth: The size of the file, the default in bytes to display the sixth paragraph: timestamp (access time, modification time, Change time) Access time: Access Timestamp modified: Modified timestamp (change the content of the data, edit the contents of the data, called modification) Change the time: changes timestamp (metadata, meta data, Edit to metadata is called change) Seventh: file name in Linux, with a. Character as the first character of the filename, is the hidden file-A: Show all files, including hidden files-A: Displays all files, including hidden files, but does not include. and.-h: Display in a human-readable way-D: Replace the property output of the internal sub-file with the properties of the folder-r: Reverse Display-R: Recursive display (recursive)-Z: Show file security context

• Cat

View Files
-N: Give all line numbers -B: no blank line numbering
Reverse display of TAC Cat

• Head

Head 3 head 3head: View 50 bytes head -C 1b: View the contents of a sector 512 bytes

• Tail

start viewing from the end. Option analogy head-F: Content changes at the end of a real-time monitored file

• More

Page shows the contents of the file only to look back

• Less
• Whereis

Displays the binary file of the command, the Help manual path

• which

To see where the file is, only the binary file path is displayed

• Whatis

Show Help manual Path only

• Stat

View file properties (Access time, modification time, change time)

2. Directory operation

• Pwd

Show working directory (absolute Path) The default working directory is the home of the/root,root user (the host directory), and the first directory where the default user logs in is the host directory

• Cd

Switch working directory
If there are no parameters, then the default parameter is the user's host directory
CD ~: Switch to the host directory
CD-: Switch to the working directory you used last time

• Mkdir

Create a Directory

mkdir-p: Create a parent record before creating a subdirectory -V: Displays the Create folder verbose procedure command expansion function, using {}, separated by commas

• RmDir

Delete directory (only empty directory) if a directory is only. and., then you think this directory is empty
rmdir [OPTION] ... DIRECTORY ...

• Rm

Removed from

RM [OPTION] ... FILE ... Option:-r: can delete directory -F: Force delete

• Type

Distinguish whether commands are internal or external commands

Get help internal command: Helper internal Command external command: Mans  Info--help

3. File editing

• Echo

-N: Do not output line break symbols
-E: Make backslash effective

• Nano

text Editing Tool, enhanced version of Pico^: Caret 1. Typically, the CTRL key is equivalent to 2in edit mode. In other uses, there are different meanings, such as: can take counter , you can indicate that line breaks are default at the beginning of a line, a newline character is equivalent to a byte ctrl+o Save Ctrl+x exit

• Touch

Changes the timestamp of the file. A file is created when the file does not exist
-A: Only modify the access time of the file
-M: Modify only the file modification time
-C: Do not create files

4. Time command

• Clock

Hardware time

• Date

System time

Set Time:1.DateDay of the month and year. SecondsDate 091703282015Thu Sep - Geneva: -:xxCst -2.Date-S "Year/month/days: minutes: Seconds "Date-S"2015/09/17 15:32:11"Thu Sep -  the: +: OneCst -3.Date+%y

• Hwclock

RTC: Real -Time clock-s synchronizes hardware time to system time -W  time to synchronize system time to hardware time touch defaults from system time

• BC Calculator
• Cal: Calendar

5. Text Processing

• Cut

Remove sectionsfrom all line of files-d indicates delimited, default space 1  first column eg:cut1 /etc/passwd
Cut-d:-F 7/etc/passwd | Sort | Uniq-c

• Sort

Sort lines of text files sort, default order ASCII encoding -N: By number size, from small to large -r: Reverse -t: Indicates the separator symbol -k: Indicates the operating area /c5>-u: If there is more than one duplicate of the content is displayed as a line, equivalent to the Uniq command sort3 /etc/passwd

• Uniq

sort -u-C: Counts the number of consecutive rows of duplicates -u: only output unique rows (discontinuous repetition)

• Tr

Character Set Conversions TR ' AB ' ' AB ' </etc/passwd -to-bit replacement

• Wc

Word counter WC byte  for file-l displays only the number of rows-w   displays only thenumber of characters-C shows only the character Count WC /etc/passwd  1427 /etc/passwd

"Linux file View, operation"