erd symbols

character. Equivalent to ' [^a-za-z0-9_] './xnMatch N, where n is the hexadecimal escape value. The hexadecimal escape value must be two digits long for a determination. For example, '/x41 ' matches ' A '. '/x041 ' is equivalent to '/x04 ' ' 1 '. ASCII encoding can be used in regular expressions:/numMatches num, where num is a positive integer. A reference to the obtained match. For example, ' (.) /1 ' matches two consecutive identical characters./nIdentifies an octal escape value or a backwar

HTML Original Code Show results Describe Less than sign or display marker gt; > Greater than sign or display marker amp; Can be used to display other special characters quot; “ Quotes reg; ? Already registered copy; ? Copyright trade; ? Trademark ensp; ? Half Blank bit em

Binary conversion rules: binary Symbol Bin (), Oct (), Hex () + Pending format number 10 binary → other binary1 #Dec2bin2 #decimal to binary: Bin ()3>>> Bin (10)4 '0b1010'5 6 #dec2oct7 #Decimal to octal: Oct ()8>>> Oct (10)9 '0o12'Ten One #Dec2hex A #decimal to 16 binary: Hex () ->>> Hex (10) - '0xa'2 binary → other binary1 #bin2oct2 #Binary to octal: Oct ()3>>>Oct (0b1010)4 '0o12'5 6 #Bin2dec7 #Binary to decimal: Int (' Number of binary formats ', 2)8>>> Int ('1010', 2)910Ten One #Bin2Hex A

1, it is well known that the regular expression if used properly, its practicality is quite strong, basically all the pre-research is to support the regular expression, but the support of the grammar is different.2, in the actual application, we may need to intercept the first special characters encountered before the text, at this time need to use the regular expression, after all, the special symbol so many, if someone really use multiple if to operate, can only say refreshed my cognition!Not

* Multiple? 1 x# annotation Characters\ de-Righteous characters| Pipe character$ as a prefix for variables, used for variables!$ using the last parameter of the previous command; Used in the middle of two commands to write in one line~ User's Home directory command dropped into the background like sleep > Redirection>> Chasing heavier orientation2> Error Redirection2>> Error Append redirect[] denotes one of the ranges such as [0-9]This article from the "Linux" blog, reproduced please contact the

X. This is equivalent to "X", which is also equivalent to ' X '. \ is usually used to escape double quotation marks (") and single quotation marks (') so that double and single quotes are not interpreted as special meanings.　　2.7 Anti-quote (')　　cp 'mkdir back ' test. SH ls　　2.8 Colon (:)2.8.1 An empty colon is equivalent to "NOP" (no op, a command with nothing to do). Can also be thought of as true of the shell's built-in command. #!/bin/bash while :do echo"endless Loop " DoneEquivalent t

* Wildcard #注释 \ escape Character | Pipe character $ variable character; command delimiter!! Executes the previous command!$ the last parameter of the previous command ~ home directory Command Background execution> correct override redirect >> correct append redirect (cannot redirect error result)2> Error override redirect 2>> error append redirect redirect[] single character match range such as: [0-9a-za-z]Special symbols in 1.4-shell

* As a wildcard character, you can represent multiple characters, such as *.txt? wildcard character, which represents only one such as. TXT a.txt# in the shell script, #放在行首, the bank does not take effect\ Caret, \ Revert special characters to normal characters| Pipe break throws the command result before the symbol to the command following the symbol$ as the identifier before the variable! $ represents the last variable of the previous commandoften used in the middle of two commands~ User's hom

Use the modifier keys to viewThe keys, like command, option, control, and shift, are called modifier keys under the Mac, and generally they are used to assist in input or modifier keys that are used as shortcut keys.Open "System Preferences", click "keyboard → keyboard → modifier key" To see these modifier keys, such as Caps Lock is?, control is?, the command is?, of course, here you can customize the keyboard mapping, For example, the command key is mapped to the control key, the control key is

output: Command 1 >/dev/null 2>error ; Ignore All output: command 1>/dev/null 2>/dev/null1, 22 kinds of information can also be redirected, so this: command 1>output 2>1 indicates that the error output is also redirected back to standard output, that is, both of the information is saved to output. Then why not write command 1>output 2>output ? The answer is no, do not look at the output to/dev/null can, but if you write the same file name can cause a conflict, so if you want to keep only the a

corresponding dynamic library in the linker's dependencies[8] The following error is usually caused by a dynamic library does not have a package come in. __impProjectRun.obj:error LNK2019: unresolved external symbol __imp__starthistorylocalmodule, the symbol in function "Protected:virtual int __thiscall Hirtdb::cprojectrun::D ostart (void) "([email protected]@[email protected]@MAEHXZ) is referenced[9]error LNK2001: unresolved external symbol __IMP___CRTDBGREPORTWProject Properties, c/C + +, cod

Give you a full, you in the Linux environment to try to understand more:The execution name of this program$n the nth parameter value of this program, n=1..9$* all parameters of this program, this option can have more than 9 parameters.$# the number of parameters for this program$$ the PID of this program (the current process ID number of the script run)$! PID of the previous background instruction (process ID number of the last process running in the background)$? Executes the return value of th