SEARCH KEYWORD -- /dev/null


  Check whether a remote server port is open on Linux

As a system administrator or network engineer or application developer, there is a need to check whether a port on remote server is open so that you can tell whether the service under check is running or not. In this post, we would cover a few methods to check whether a remote server port is open or not on Linux. telnet telnet is the most frequently used command on both Windows and Linux to check port. The simple usage for this command is  telnet [host] [port] When the port is open, the o...

   LINUX,TELNET,PORT,NC,NMAP     2017-12-23 11:45:20

  Algorithm : Delete middle node from singly linked list

Questions about singly linked list are frequently asked during technical interviews. Today we will share with you one algorithm question about singly linked list. Here is the problem description. Assuming the only information you are giving is there is a pointer to a middle node of a singly linked list, no other information about the linked list is given. Please delete this node and don't affect the structure of the linked list. Initially you may think this question is easy if you know the hea...

   ALGORITHM,C,LINKED LIST     2015-10-30 05:21:25

  About tmpfs

tmpfs is another confusing name in Linux kernel, its implementation is in mm/shmem.c, shmem has no relation to tmpfs at first glance although we know tmpfs is based on memory. We can understand why we use this name by seeing where this is used. In a desktop Linux system, tmpfs is loaded usually: % grep tmpfs /proc/mountsdevtmpfs /dev devtmpfs rw,seclabel,nosuid,relatime,size=1958956k,nr_inodes=489739,mode=755 0 0tmpfs /dev/shm tmpfs rw,seclabel,nosuid,nodev,relatime 0 0tmpfs /run tmpfs rw,seclab...

   tmpfs,Linux,file system     2013-06-14 12:10:56

  Tips and tricks about JavaScript from Google

JavaScript is now a very popular client side language. It's flexible, powerful but easy to make mistakes. So good programming style is better for you to write efficient and readable JavaScript codes. Here are some tips and tricks about JavaScript from Google. True and False Boolean Expressions The following are all false in boolean expressions: null undefined '' the empty string 0 the number But be careful, because these are all true: '0' the string [] the empty array {}&n...

   JavaScript, Google, Coding standard     2013-02-26 23:11:03

  Binary tree iterator algorithm

Binary tree pre-order,in-order and post-order traversal are basics in algorithm and data structure.And the recursive binary tree traversal is a classical application of recursion. We define a binary tree node as : // C++ struct Node { int value; Node *left; Node *right; } In order binary tree traversal can be: // C++ void inorder_traverse(Node *node) { if (NULL != node->left) { inorder_traverse(node->left); } do_something(node); if (NULL != node->righ...

   Binary tree,Iterator,Traversal     2013-07-14 21:51:09

  Recover deleted file in Linux EXT3 file system

Environment : CentOS 5.3 x86_64, /dev/sdb1 is the data segment /data0. EXT3 file system. Problem : /data0/tcsql/cankao/phpcws-1.5.0/httpcws.cpp is deleted mistakenly and httpcws.cpp is not backed up. It will take much time to rewrite this program again. So we must recover it back. debugfs is feasible in EXT2 file system, but in EXT3 file system, it's not very useful. There is one open source software called ext3grep which can help us recover deleted file in EXT3 file system. The recovery steps a...

   Linux,EXT3,File recovery     2013-08-16 07:06:45

  Algorithm : Reverse singly linked list

Questions about singly linked list are the lovers of interviewers during interviews given the characteristic that singly linked list is one-directional list and it's difficult to get the previous node of one node without some buffering tricks.  In this post, we will demonstrate one of the most frequently asked question about singly linked list -- Reversing the singly list. Given the first node of a singly linked list, reverse the singly linked list. For example : A->B->C->D After ...

   ALGORITHM,INTERVIEW,C     2015-10-31 11:38:35

  Different types of keystore in Java -- Windows-MY

Windows-MY is a type of keystore on Windows which is managed by the Windows operating system. It stores the user keys and certificates which can be used to perform cryptographic operations such as signature verification, data encryption etc. Since it's a kind of native keystore, Java doesn't have a general API to access it. To help Java applications access the keys and certificates stored in Windows-MY keystore, Java provides a separate API -- SunMSCAPI. The SunMSCAPI provider is ...

   JAVA,KEYSTORE,WINDOWS-MY,SUNMSCAPI     2016-01-09 05:45:59

  A small trick on using console.log to print data in JavaScript

When debugging JavaScript application, one may frequently use console.log to print data so that it is easy to debug when issue occurs and also helps on understand the data flow. The common way of printing a variable would be something like.  let user = { name: "test" }; console.log(user); In this case it will print: { name: 'test' } This is OK when there is no much logging or the program is not complicated. But it becomes difficult to debug if there are lots of variables to be printed ...

   JAVASCRIPT,CONSOLE.LOG,DEBUGGING     2019-09-03 10:24:24

  A possible way to recover deleted files on Linux

Last week I was generating a MD5 sum for an virtual machine image on one OpenNebula server: # ls -l test.img -rw-r--r-- 1 root root 10486808576 Oct 12 02:21 test.img # md5sum test.img At the same time I was clearing the files on the server on another terminal and deleted the above image file mistakenly with : # rm test.img Since this image file is 10GB, it took some time to remove this file from the server, so I used the Ctrl+Z command to suspend the remove command. [1]+ Stopped ...

   Linux,File,Recovery     2013-11-26 07:03:37

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