Unix If File Exists

After you have finished this chapter, you will be able to do the following: Explain the purpose of the device file explain the meaning of the main number and the number of the different character devices use Lsdev to list the main numbers of kernel drivers use LS to observe the primary and secondary numbers of a device file Use Ioscan to list device files associated with a specified device using ISSF to describe the characteristics of a device file. Assign a disk, tape, or CD device file name, determine the target number of the control card and the target address of the associated device assigned to a terminal or a Xiandai device file ...

The .htaccess file allows us to modify some server settings for a particular directory and its subdirectories. Although this type of configuration is best handled in the section of the server's own configuration file, sometimes we do not have permission to access this configuration file at all, especially when We are on a shared hosting host, and most shared hosting providers only allow us to change server behavior in .htaccess. .htaccess file is a simple text file, note the "." before the file name is very important, we can use your favorite text editor ...

This paper is an excerpt from the book "The Authoritative Guide to Hadoop", published by Tsinghua University Press, which is the author of Tom White, the School of Data Science and engineering, East China Normal University. This book begins with the origins of Hadoop, and integrates theory and practice to introduce Hadoop as an ideal tool for high-performance processing of massive datasets. The book consists of 16 chapters, 3 appendices, covering topics including: Haddoop;mapreduce;hadoop Distributed file system; Hadoop I/O, MapReduce application Open ...

This paper introduces how to build a network database application method by MySQL of the golden combination of Web database, PHP is a server-side embedded hypertext Processing language similar to Microsoft ASP, it is a powerful tool to build dynamic website. While MySQL is a lightweight SQL database server that runs on a variety of platforms, including Windows NT and Linux, and has a GPL version, MySQL is considered the best product for building a database-driven dynamic Web site. PHP, MySQL, and Apache are Linux ...

S3QL is a file system that uses something like Google Storage, http://www.aliyun.com/zixun/aggregation/2467.html ">amazon S3 or OpenStack storage devices to store all of the online data. It supports Amazon S3, as well as any SFTP server, and effectively provides a dynamic and infinitely capable hard drive that can be accessed from any computer that has access to the Internet. S3QL provides a standard ...

The simplest way to compromise is to have your password written somewhere, and there is no guarantee that no one else can see it except you. If someone gets your password and your private key file, the entire encryption system will be silent. Another old topic is the password not too simple, note that PGP is "password" passphase, rather than "password" password that is, you can include multiple words and spaces in the password. A wily attacker may use a famous book to find your password. So in order to get a good and difficult to guess password, you can sporogenous some sentences or find ...

Read the file & http: //www.aliyun.com/zixun/aggregation/37954.html "> nbsp; read the file internal working mechanism see below: The client calls FileSystem object (corresponding to the HDFS file system, call DistributedFileSystem object) Open () method to open the file (ie the first step in the diagram), DistributedFileSyst ...

The intermediary transaction SEO diagnoses Taobao guest cloud host technology Hall "the SEO new person to the website on-line" regarding the space choice to write a little, therefore today's year bin detailed to speak the basic knowledge of the space. 　　SEO rookie in the selection of host space, the main view of the following aspects of the space package, in the contact host their own site type, picture class or text class, the user in the south or north, but also economic strength, choose the right virtual host space to build the station. Host space: Web space is what you buy ...

& nbsp; ZooKeeper is a very important component of Hadoop Ecosystem, its main function is to provide a distributed system coordination service (Coordination), and The corresponding Google service called Chubby. Today this article is divided into three sections to introduce ZooKeep ...

The intermediary transaction SEO diagnoses Taobao guest Cloud host Technology Hall website completes, the maintenance and the management becomes the work which needs to carry on continuously. 　　In this chapter, the site will be optimized for internal links, efficient maintenance, PR upgrade way to introduce. First, optimize the internal links of the site two, the site efficient maintenance of three common sense three, improve the site PageRank have a coup four, site exchange links to beware of counterfeit five, against the vulgar ban on the site's illegal content six, simple configuration let Web server impregnable ...