learn unix shell scripting

1. Write more comments in the script This is a recommended practice that can be applied not only in shell scripts, but also in all other types of programming. commenting in a script can help you or others to read your script Learn about the different parts of the script. Comments are defined with a # number.2. when the script exits when the run fails Sometimes, even if some commands fail, bash may c

The main contents of this section:Top command to count CPU utilizationOne, problem analysisMySQL is multi-threaded under Linux and can only distribute multiple threads to a single CPU.Therefore, using a small server, or PC server, multiple CPU utilization is not high.Basically one or two are in use.This section shares the statistical CPU utilization method, for everyone to learn the reference.Related reading:View Linux system Resource Usage (top, free

Unix/linux Shell Programming Combat: Using embedded documents here documents First, here documents (embedded documents)Here, documents. As a way of redirecting, instructs the shell to start reading the output at the current location of the source file until it encounters a text row that contains only one word. All lines of text that are read in this procedure ar

Shell scripting is an essential skill for Linux OPS engineers and a very important skill, so it's only good to learn shell programming well. Basic grammar I will not speak, learn the C language of these languages, a little bit to understand the basis of

goes back to maintain the heap of code, it is difficult to forget some special characters. There are too many special rules to be remembered when you fully master bash scripts! In addition, various shell implementations are deeply immersed in various inconsistencies due to complexity. No wonder many people think shell syntax is messy. In short, it will not cause any obstacles to communication with other p

Here I share is learning the computer Shell scripting language method, you may not be in the software industry, but I suggest also look, because I did not say what technical details, the main share is to refine the generality of the method, which is useful for learning anything. Of course, if you're curious enough, suggestions can also be tried in the following ways, because scientists have predicted: the

the Linux system, and why do users automatically have these variables when they log on to the shell?/etc/profile: This file presets several important variables, such as path, USER, LOGNAME, MAIL, INPUTRC, HOSTNAME, Histsize, UMAs, and so on./ETC/BASHRC: This file is mainly preset umask and PS1. This PS1 is the string of characters we have in front of the command, such as the author's Linux system PS1 is [[email protected] ~]#, you might as well look

environmental changes to the parent shell. 2. Use parentheses () Running a command in () also opens a child shell. So do not randomly write () in Linux to change the priority, unless it is escaped, and the parentheses after the turn to have a space between the contents of the parentheses. [Email protected] tmp]# echo $BASH _subshell 0 [Email protected] tmp]# (echo $BASH _subshell) 1 ? Description opens a

Fgrep. These return values make it possible to perform aself-initiated text processing. I used the Egrep tool in the example above. is the extension of grep, a lot of other ways to use this tool and the above introductionSome of the inadequate places you can go to the encyclopedia to find out, in fact, some of the more advanced tools also support this expression. I'll be in the knot.The blog is again introduced.I personally think that the rote of these characters is inappropriate. We should

redirect to generate a patch file:[Email protected]:~/dl$ diff-u version1.txt version2.txt > Version.patch[Email protected]:~/dl$ cat Version.patch---version1.txt 2015-12-28 19:16:28.866869790 +0800+ + + version2.txt 2015-12-28 19:17:12.078872041 +0800@@ -1,5 +1,5 @@This is the original text-line2-line3+lin2Line4Happy hacking!+gnu is not UNIXUse the following command to Patch:[Email protected]:~/dl$ patch-p1 Version1.txt Patching file Version1.txt[Email protected]:~/dl$ cat Version1.txtThis is

Unix shell learning detects the Returned code. When running any command, linux returns the response related to the execution of the previous command, called return code. How can we get back to the code? Simple. use $? You can view it. You can view it. If the command is successfully executed, the return code is 0. If the command is not successfully executed, a value other than 0 is returned. We can use a sma

Recently saw the shell script. The shell script has been used many times in a lot of ready-made kits. In short, the effect of this thing is to integrate a series of operations.• Integration makes a set of work more modular and standardized.• Batch processing is much faster than manual operation.The shell script is a script, but it is quite different from some reg

Tags: distinguishing string roo Interactive process%s usage definition function efficiencyFirst, Shell script introductionThe shell is a scripting language, and the shell is a collection of system commands1, can use logic judgment, cycle and other grammar;It's a bit like C language, but it's fundamentally different.2,

Follow the Runoob website tutorial to learn the notesLike other languages, the shell can also contain external scripts. This makes it easy to encapsulate some common code as a standalone file. Shell files contain syntax in two forms . FileName #也就是一个英文句号后面跟着想要包含的文件名, notice that there is a space separating the middle SOURCE filename While experi

the symbol to add content to prevent omission.Pairs of symbols include: {}, [], ', ', ', ', '(2) The brackets [] must have at least 1 spaces at each end.(3) For the Process Control statements, you should write the format once, then add the content. Such as:If statement:If condition contentThenContentFiFor loop:ForDoContentDoneHint: while and until, case, and so on statements are also the same.(4) Make the code easier to read by indenting.(5) The value of the string definition variable for a reg

legitimate email address, the work can be done in the Web page JavaScript, or in the website backstage program, such as PHP, Perl, Python, Ruby, Java, or C, all these words? Support for regular expressions, it can be said that the current programming language does not support regular expressions is very rare. In addition to the programming language , many UNIX commands and tools also support regular expressions such as grep, VI, SED, awk, Emacs, and

Learn from this section the main control statements, loop statementsComments, Shell Multiline commentsThe Shell line comment is simple, just add # at the beginning of each line, but he does not provide a special multi-line comment method, so we use a clever way to multi-line comments, using the EOF delimiter to multi-line comments, as follows: 1 #! /bin/sh 2 3

Previous Edit CommandA: Append data after the current cursorO: The next line of the cursor inserts dataDW Delete a Wordd$ Delete to end of lineDD: Delete Row, 5dd delete 5 rowsThe use of backspace and delete keys in normal mode is not recognized.10.1.4 Copy and pasteDD can be pasted with p after deletion.The copy command is Y,YW copy a wordy$ Copy to end of lineThen use p to paste10.1.5 Find Replacement: s/old/new/g a line command to replace all old, which is replaced only on one line: N,ms/old

command through the path sequence in the variable that is recorded in path, and if it is not found, the system will prompt you to "command not Fount" again, because under Linux, all executions require code execution. And as mentioned above, the real shell and Linux communication is the correct login to Linux, you will have a bash execution program, which is the bash to communicate with Linux, before you log in to Linux need some variables to provide

Tags: Shell linux bash Tutorial script videoThe shell is a bridge between the user and the Unix/linux operating system. The user can either enter command execution or use shell scripting to do more complicated operations.　　In the increasingly perfect GUI today, in the system