[Reading Notes] Linux commands, editors, and shell programming

[Reading Notes] Linux commands, editors, and shell programming-general Linux technology-Linux programming and kernel information. Read the following for details. Author: Hong haihui
Mark G. Sobell of Linux Command, editor and shell programming translated by Yang Mingjun Wang Fengqin to Tsinghua University Press

2007-12-24
Terminal handling characters:
Ctrl + z suspended. You can use fg to switch to the foreground. jobs can view background tasks;
Ctrl + w delete words;
Ctrl + u deleting rows ctrl + x seems ineffective;

Positioning tool:
Which only searches for the specified path and only reports the first found path;
Whereis in the standard path, show all;
Type determines whether the file is a built-in command;
Apropos keywords
Whatis completely matches the keyword;

Symbolic Link:
The built-in command pwd displays the Link name;
Tool (/bin/pwd) display path;
Info bash builtin list built-in commands;

2007-12-25
Use of vim:
Ctrl + w delete words;
Ctrl + h Delete row ctrl + u;
: Redo ctrl + r undo;
Ctrl + l refresh;
Vim-r check the swap file;

Move the cursor in command mode
Move spaces h and l; Ff
Move the word Ww W to separate characters by Spaces
Move row j k
Sentence ()
Segment {}
Screen H M L

Delete
Delete dG to the end;
D1G is deleted from the beginning;
D0 starts from the row;
~ Modify the case sensitivity;

Replace
1 ,. Starting to the current row;
., $ From current to end;
1, $ or % All;
: 1, $ s/ten/te/g replace all 10 of all rows with te;

2008-01-05
Array variables:
Assignment
NAMES = (max helen sam zach)
NAMES [1] = fly
Reference Value
# Echo $ {NAMES [2]}
Sam
------------------------------
Subscript

Difference from:
The function is to extract the entire array, but the working mechanism of double quotation marks is different:
@ Copy the original array to the new array, which is the same as the old one;
* Copy the original array as an element to the new array.
Example:
A = ("$ {NAMES

}")
B = ("$ {NAMES [@]}")
Use declare-a to display the array content
[Root @ Test ~] # Declare-
Declare-a NAMES = '([0] = "max" [1] = "helen" [2] = "sam" [3] = "zach ")'
Declare-a A = '([0] = "max helen sam zach ")'
Declare-a B = '([0] = "max" [1] = "helen" [2] = "sam" [3] = "zach ")'

Echo $ {# NAMES

} Number of elements
[Root @ Test ~] # Echo $ {# NAMES

}
4
Echo $ {# NAMES [0]} element length
[Root @ Test ~] # Echo $ {# NAMES [0]}
3
---------------------------------
(Count = count-1). Make sure that the shell is regarded as an arithmetic expression and the variable does not need to be $
$ Process ID to create a unique file name;
$0 command itself;
$! Background process PID;
$? Exit status;
$ # Number of parameters except the command itself;
$ * And $:
$ * Treat all parameters as a whole (one parameter );
$ @ Is the same as the original one;
Subscript

[@] Same
----------------------------------
Shift left shift command to get any parameter, cyclically scan command line;
Set the initial command line parameter value;
Set $ (date)
Set date
-----------------------------------
:-Use the default value $ {name:-default}
: = Default value $ {name: = default}
: Built-in command assignment is not executed: $ {name: = default}
:? The error message is displayed, and status 1 is returned. shell does not exit; $ {name :? Message}
------------------------------------
Path Operators
# Remove the minimum prefix;
# Remove the maximum prefix;
% Minimum removal prefix;
% Remove the maximum prefix;
Example:
[Root @ Test ~] # Test =/usr/local/src/proftpd-1.2.10.tar.gz
[Root @ Test ~] # Echo $ {test}
/Usr/local/src/proftpd-1.2.10.tar.gz
[Root @ Test ~] # Echo $ {test #/*}
Usr/local/src/proftpd-1.2.10.tar.gz
[Root @ Test ~] # Echo $ {test ##/*}
[Root @ Test ~] # Echo $ {test % /*}
/Usr/local/src
[Root @ Test ~] # Echo $ {test % /*}

[Root @ Test ~] # Echo $ {# test}: number of characters displayed
36
-------------------------------------
Sed usage:
Parameters:
-N: in addition to the p command;
-I save the changes to the file;
Command:
D. Delete the entire row;
N displays the current row and reads the next row from the input;
A. append the file after each line and use \ line feed;
Append before line I;
C replacement file (entire line );
S replacement address;
W. Redirect to the new file;
R: after appending rows;
Q: exit;
Control Structure:
! NOT $! D except the last line;
{} Command Group; separated
Pattern and Hold:
Pattern: Work Platform (Save the row you just read );
Hold: Temporary Workspace
H p-> H: append a line break and content to H
H P-> H replace P zone with H
G h-> P append a line break and content to G
G H-> P replace H zone with P
Example:
Sed '5 Q' filename displays the first five rows;
Sed '2 a test' insert a linefeed and test after row 2nd of filename;
Sed '/the/n; P' file all match the not displayed;
Sed's/^./\ t &/'the first line of filename is not a space to insert a tab;
(^.) The beginning of the line is not a space;
S/^/\ t/Insert a tab at the beginning of the line;
S/* $ // delete all spaces at the end of the row;
Sed 'G' filename insert an empty row after each row;
Reverse Order:
2, $ G
H
$! G
------------------------------
Cat
-A (-vET)
-B Numbers non-empty rows;
-N: numbers all rows;
-S removes unnecessary blank rows;
Cut
-C
-D separator;
-F
Example:
[Root @ Test sh] # ll | tr-s ''' | cut-f 5, 9-d''
2.3 K
2.2 K B
4.0 k bk/
436 ip.1
452 ip.2
264 ip.
85 K ip. list
22 K ipList. temp
486 sample. sh *
9.9 K selectInfo. sh *
4.0 K temp/
Tr-s converts multiple spaces into a single space;

[Root @ Test 20080114] # grep-n' ^ 'test
1:
2: B
3: c
4: d
'^' Matches all rows;
-N: numbers all rows.

[Root @ Test 20080114] # grep-h a * | sort | uniq-c
2
-H: the file name is not displayed;
Uniq-c displays duplicate rows only once and counts the number of repeated rows;

[Root @ Test 20080114] # vi $ (grep-l 'A '*)
2 files to edit
Edit multiple matching files;
-L name of the matched file;

# Kill-9 0
For common users, it is equivalent to logging out;
Please use it with caution if root is equal to shutdown;
--------------------------------
Ls parameters:
-A: All files except... are displayed;
-F displays file features;
-R inverse direction;
-T: Based on the modification time;
-X rows are displayed;
-A file is displayed in one row;
--------------------------------
Sort
Parameters:
-B. Exclude spaces and tabs before fields;
-F converts lowercase letters into uppercase letters (in front of uppercase letters );
-N arithmetic sorting. The negative number and decimal point make sense;
-R inverse direction;
-T x separator x;
-U duplicate rows are displayed only once;
-K start [, stop]
Note:
Upper case before lower case;
The blank space is before;
The first query is not the same, and the second query is not performed;
Example:
# Sort -- key = 2 test 2nd field;

# The sort-k 2-f test 2nd Field, which is in upper case;

# Sort-k 2-B test 2nd Field. the blank spaces and tabs in front of the field are ignored;

# Start with 3.4 characters in the sort-fb-k 3rd test 4th field;

# Sort-B-k 3.4-k-2f test
First time: 3rd characters of the 4th Field
Second time: the 2nd field, which is in upper case;

# Sort-k 1-k 5 test
The first field, that is, the end field, and the fifth field;
However, if the comparison for the first time is not the same, the comparison will not be performed for the second time;

# Sort-k 1, 1-k 5 test
The first field,-k (the first character of the first field to stop: the first field)
Perform the fifth field;

# Sort-u-k 1f-k 1 test
Perform Two-time comparison. When fields with the same case are found;
------------------------------
Regular Expression:
Asterisk:
/(. *)/The longest matching with parentheses;
/([^)] *)/Minimum matching with parentheses;

Empty regular expression:
/\ (Test \)/is the same as/test;
/A \ (B * \) c/is the same as/AB * c;

Replacement string:
& String matching of symbol and regular expression matching
\ N escape number
Example:
: 1, $/\ ([^,] * \), \ (. * \)/\ 2 \ 1/
1, $ all rows;
\ ([^,] * \) Is the same as [^,] *, and matches any string except the comma;
\ 2 represents the regular expression in 2nd parentheses;
--------------------------------
Extended Regular Expressions:
+ Match the first one or more characters;
? Match the first 0 or 1 Characters
Example:
/AB + c/abc abbc
/AB? C/ac abc
/(AB) + c/abc ababc
/(AB )? C/c abc

/AB | ac/AB ac abac
/^ Exit | ^ Quit/start with Exit or Quit
/(D | N) \. Jones/D. Jones N. JOnes

Represented by \ | in vim |

Special characters:
. Single character;
* And * The first 0 or multiple characters;
\ <Start of the word;
\> End of the word;