Shell Special Symbols

First, shell special symbol Cut command
A command that intercepts a field: cut

-D: followed by delimited characters, separated by single quotation marks
-C: followed by the first few characters
-F: The next section is followed by the number of blocks
-D followed by the delimiter character, where a colon is used as the split character, and-F 1 is the first paragraph, and the space between-F and 1 is optional.
The-C can be either 1 digits n or an interval n1-n2, or multiple digits n1,n2,n3

Second, Sort_wc_uniq command
1. Sort for sorting
-N: Sorting with pure numbers
-R: Reverse Sort

2. Order: WC
The number of rows, characters, and words used to count the document, and the commonly used options are:
-L: Count rows
-M: Statistics of characters
-W: Number of statistical words

WC does not follow any options, directly with the document, it will be the number of rows, words, characters in turn output
3. Command: Uniq
To repeat a row, often used with the sort sort command. The premise of using Uniq is to sort the files first, otherwise it won't work.

-C: Count the number of repeated rows and write the number of lines in front

Iii. Tee_tr_split Order
1. Command: Tee
-A Append

followed by the file name, similar to redirect ">", but the specific gravity of a function, the file is written in the following file, while also displayed on the screen

2. Command TR
The most common is to capitalize the lowercase: tr ' [A-z] ' [A-z] '

3. Split command
Cutting documents
Common options:
-B: Divide the document by size in bytes
-L: Split document by number of rows

Four, the shell special symbol under
1, variable prefix 2, '! ' represents the last variable in the previous hit
3,; Semicolon. To run two or more commands in a row, you need to add a ";" between the commands.

4, ~ User's home directory, regular expression means match

5, & placed behind the command, will throw the command in the background

6, > Output redirect,>> append output redirect,2> error redirect,2>> error append redirect correct and error output redirect &>

7, [] brackets, one of the specified characters, [0-9],[A-ZA-Z],[ABC]

8, | | expressed or,&& expressed and

Determine if a directory exists, such as:
[-D Amolinux] | | mkdir Amolinux

(If the Amolinux directory exists, the subsequent Create directory command is not executed; if the Amolinux directory does not exist, execute the command to create the directory)

Shell Special Symbols