If Statement Shell Script

By completing this chapter, you will be able to do the following: Use the while statement to repeatedly execute a piece of code when the condition is true. Use the loop statement to repeatedly execute a piece of code until the condition is true. Use the interactive for statement for loop control. 1. Brief introduction to the loop objective: Repeat the execution of a list of commands. control; a return value based on a key command. Three forms: While ... do ... do loop ... do ... do.

You can use the flexibility inherent in the command shell of Linux to create scripting languages that help you simulate DOS commands in a Linux environment. 　　 　　The specific approach is as follows. If you are an IT support expert, you like the command of Windows very much, when you first use the Linux command line, you may soon find yourself confused. The DOS commands you've been familiar with for a long time don't exist in Linux. So you will find yourself facing a terrible task: to learn and be familiar with the whole ...

Intermediary transaction SEO diagnose Taobao guest Cloud host technology Lobby database optimization is a very complex task, because it ultimately requires a good understanding of system optimization. 　　Even though the system or application system does not know much about the optimization effect is good, but if you want to optimize the effect of better, then you need to know more about it. 1, the optimization of the system to run faster the most important factor is the basic design of the database. 　　And you have to be aware of what your system is going to do, and the bottlenecks that exist. The most common system bottlenecks are as follows: ...

To use Hadoop, data consolidation is critical and hbase is widely used. In general, you need to transfer data from existing types of databases or data files to HBase for different scenario patterns. The common approach is to use the Put method in the HBase API, to use the HBase Bulk Load tool, and to use a custom mapreduce job. The book "HBase Administration Cookbook" has a detailed description of these three ways, by Imp ...

Apache Pig, a high-level query language for large-scale data processing, works with Hadoop to achieve a multiplier effect when processing large amounts of data, up to N times less than it is to write large-scale data processing programs in languages ​​such as Java and C ++ The same effect of the code is also small N times. Apache Pig provides a higher level of abstraction for processing large datasets, implementing a set of shell scripts for the mapreduce algorithm (framework) that handle SQL-like data-processing scripting languages ​​in Pig ...

Code: ctrl + y Find: disable_functions found after the = added (here are prohibited in the php inside the function) Code: copy the contents to the clipboard exec, system, passthru, error_log, ini_alter, dl, openlog, syslog, readlink , symlink, link, leak, fsockopen, proc_open, popep ...

Several articles in the series cover the deployment of Hadoop, distributed storage and computing systems, and Hadoop clusters, the Zookeeper cluster, and HBase distributed deployments. When the number of Hadoop clusters reaches 1000+, the cluster's own information will increase dramatically. Apache developed an open source data collection and analysis system, Chhuwa, to process Hadoop cluster data. Chukwa has several very attractive features: it has a clear architecture and is easy to deploy; it has a wide range of data types to be collected and is scalable; and ...

Summary Today, we're not talking about complex technical implementations in Spark, just a little bit of code-behind. It's well known that Spark uses scala to develop because scala has lots of syntactic sugar on it, so many times it's time to get back the code and follow it, and Spark is based on information exchanged by Akka, so how do you know each other? Is the recipient? new Throwable (). printStackTrace In the code to read, users often ask for help in the log, reading the log ...

Summary Today we only talk about the code to read the method, do not carry out those complicated technical implementation in Spark. Surely we all know that Spark was developed using scala, but because of the large number of syntactic sugars in scala, code often follows and discovers clues. Second, Spark interacts with Akka based on how to know who Recipient it? new Throwable (). printStackTrace In the code following, we often rely on the log, and ...

MySQL has become one of the most widely used databases in the current network, especially in Web applications, which occupy the absolute advantage of small and medium applications. It all stems from its compact, safe, efficient, open licensing and multi-platform, and, more important, the perfect combination of--php with one of the three web languages. Unfortunately, a default installation of MySQL, because the root password is empty and the program vulnerabilities caused by the overflow, so that the installation of MySQL server is a frequent target. What is more serious is that the database is often destroyed after the attack, causing disaster easily ...