What Is The Use Of Echo Command In Unix

8.if statement syntax: (for one-way Judgment branch) if list A then list B fi Example: if Test-s funfile then echo funfile exists fi echo Hello if structure is a value based on command return Process Control mode. If the test command returns a value of 0, a specified list of commands is executed, and if the command returned with a value other than 0, the specified command list is ignored ...

By completing this chapter, you will be able to do the following: Describes the effect of a return value in a conditional branch statement. Use the test command to parse the return value of a command. Use the IF and case structures in a shell program. &http://www.aliyun.com/zixun/aggregation/37954.html ">nbsp;1. Return value shell variable"? "To save the return value of the last executed command: 0: ...

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 ...

To complete this chapter, you can do the following things: Use a referral mechanism on the command line to ignore special meanings of special characters 8.1 introduces many characters in the shell with the meaning of "special":-Space-Enter-$-#-*-< > Reference eliminates (ignores) the special meaning of these characters. In Unix systems, some special characters have special meanings for the shell, for example, spaces are delimiters for commands and arguments; carriage returns send a signal to the shell to execute the command, and the $ symbol is used to show and change ...

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 ...

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.

The intermediary transaction SEO diagnoses Taobao guest Cloud host technology Hall Internet is becoming more and more popular today, PC security not only requires the prevention of computer viruses, but also to improve the system to resist the hacker's ability to attack the illegal intrusion, and to improve the confidentiality of remote data transmission, to avoid illegal theft in transit.  In this paper, we simply analyze some situations that may occur when constructing Web server, hoping to arouse attention. &nb ...

The 7.for statement loops through each entry in the list, giving Var the next entry in the list each time the loop completes, until the end of the last entry is completed. Syntax: example: for VAR in list $ cat Test_fordo For X in 1 2 3 4 5 list A Dodone ...

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 ...

Simply put, Linux is a set of http://www.aliyun.com/zixun/aggregation/17944.html "> free to use and freely propagated Unix-like operating systems, which are mainly used for intel-based x86 series CPU computer. This system is designed and implemented by tens of thousands of programmers around the world. 　　The aim is to establish UNIX-compatible products that are freely available to the world without the copyright of any commercial software. Linux ...