common knowledge book

, use: Grep-n "Xiaoluo"/home/test.txt (query the number of rows in the Test.txt file that the information is in and change all text) find "Search files and directories" such as: Find/ Home-name Test.java (Find files named Test.java under the home folder or all subfolders in home) REDIRECT Commands >, >>, If a a.txt file is present, the previous information is overwritten) ls-al/etc>> aa.txt (Append the list information of etc to the Aa.txt file information) Enter information from the file AAA Ce

in the/etc directory and are of the normal file type [[emailprotected]~]#find/ etc/-size+1m-typef/etc/selinux/targeted/policy/policy.29/etc/udev/hwdb.bin/etc/ brltty/zh-tw.ctb[[emailprotected]~]#6, find files with no write permission for all users in/etc directory [[emailprotected]~]#find/etc/ -not-perm/222[[emailprotected]~]#find/etc/-not- perm+222[[emailprotected]~]#find/etc/-not-perm /222|wc-l23[[emailprotected]~]#find/etc/-not-perm+ 222|wc-l23[[emailprotected]~] #7, find at least one class

! = STR2STR1 = = str2So what's the output of the second program? The first way we talked about this is not to take the initiative to add the object to the string pool, but with an exception, calling the Intern () method manually will force a reference to the object to be added to the string pool. So the result of the second procedure isSTR1 = = str2"Question 4"differences and linkages between String pool and const poolKnowing the Java memory model, there is an area in Java memory called the meth

Seq.txtBananaApplePearOrangeSort Seq.txt?AppleBananaOrangePear? (2) sort-u Remove duplicates(3) Sort-r in reverse orderCat Number.txt13524Sort-r Number.txt54321(4) The SORT-N option is sorted by numerical size(5)?? The-t option for sort and the-K optionIf there is a file content like this, the cat Facebook.txtbanana:30:5.5? apple:10:2.5? pear:90:2.3? orange:20:3.4?The first column represents the fruit type, the second column indicates the fruit quantity, the third column represents the unit pri

') INSERT into" SYSTEM "." E_category "(ID, T_category) VALUES (' 3 ', ' laptops ') INSERT into" SYSTEM "." E_category "(ID, T_category) VALUES (' 4 ', ' shirts ') INSERT into" SYSTEM "." E_category "(ID, T_category) VALUES (' 5 ', ' coats ') INSERT into" SYSTEM "." E_category "(ID, T_category) VALUES (' 6 ', ' slacks ') 3. Modify the table structure: add a field; ALTER TABLE e_category add Bigcate varchar2 ( 4. Modify table structure: Add a foreign key; ALTER TABLE E_PRODUCT add constraint fk_

");Instantiate a large number of floating-point BigDecimal j = new BigDecimal ("7654321");BigDecimal k = new BigDecimal ("1234567");System. out. println("i="+i);System. out. println("j="+J);System. out. println("k="+K);System. out. println("Addition"+j. Add(k));System. out. println("Subtraction"+j. Subtract(k));System. out. println("Multiplication"+j. Multiply(k));System. out. println("Division"+j. Divide(k));Bigdecimal[] result = J. Divideandremainder(k);//retention quotient and remainderSystem

1.ls-a command will list all contents (. cache,controller.py) in the current directory;In 2..cache . Indicates that the file is a hidden file; the suffix py in controller.py represents a Python script;3.vi . Profile, which is a hidden file in which the text content # indicates that the line content is commented;4.00 * * * * * sh/root/refreshbondgoods/run.sh >> Log.log, the run.sh script is executed every 3 o'clock in the morning, the log is automatically entered into the Log.log file; (for cront

To convert an array or an object to a JSON stringJson_encode (); reverse is json_decode (); In addition to $_request,$_get,$_post, a way to obtain network request data in the form of a data stream$requestData file_get_contents ("Php://input"); $echo ($requestData); To convert a string to an array at a flag interval$arr=explode($flag,$string//$flag can be "|", "/" and so on $parm 0 $arr[0]; $parm 1 $arr [1]; ... Convert an array to a request string after url-encodedHttp_build_query ($arr);

Label:In SQL Server:1. The following query statements can be used to query to system tables (system_table), table aliases (synonym), user tables (user_table), Views (view), primary foreign key names, triggers, stored procedures, and so on, based on the different queries of ' Type ':　　　　SELECT * from SYS. OBJECTS;2. The table alias (synonym) can be queried by the following query statement:　　　　SELECT * from SYS. synonyms;3. The following query statements can be used to query the relevant user tabl