shell booter

the value of n does not change when the screen output is 21, but when the entire echo execution is complete, the value of n changes, outputting 21, 22. for this, you can easily write another test case: while [[$i-lt 10]]; Do ((i++)); echo $i |awk ' {print >> '/root/tmp/n '} '; Sleep 2; Done So why does this case see the value of N changing in real time? Don't worry, after reading this article, you will find the answer yourself. ^ _ ^ the problem with the statement (1) is that a concept under t

As already mentioned, variable names can only contain numbers, letters, and underscores, because some variables that contain other characters have special meanings, and such variables are called special variables.For example, $ represents the ID of the current shell process, the PID, as shown in the following code: $echo $$ List of special variables variables meaning $ File name of the current scr

20.16-20.17 functions in the shell The function is to organize a piece of code into a small unit, and give the small unit a name, when the code is used to call the name of the small unit directly. 格式: function f_name() { command }函数必须要放在最前面 Script Instance 1 #!/bin/bashfunction inp(){ echo $1 $2 $3 $0 $#}inp 1 a 2 Script Instance 2 #!/bin/bashsum() { s=$[$1+$2]

Programs on the Linux server update the MySQL database every day, so remember to write a shell script, combined with crontab, to back up the database regularly. Actually very simple, the main is to use the mysqldump command with MySQL. #!/bin/bash # Shell script to backup MYSQL database # to backup nysql databases file To/backup dir and later pick up By your # script. Can skip few databases from bac

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 future of the world is a software definition

Environment: SSH server:192.168.100.29 server.example.comSSH client:192.168.100.30 client.example.com Create secret key authentication through root user to implement Shell script management, distribution, deployment First, the client side creates the secret key pair and distributes the public key to the SSH server that needs to be logged on Note: The public key is equivalent to a lock, the private key is equivalent to a key, we here is equivalent

The recent systematic study of the shell function, the overall sense of the root of the other language function is similar, but it also has its own characteristics One, the call function must be defined after the function, or it will be the error Copy Code code as follows: Fun Fun () {echo "AAAAAA"} Fun The returned results are as follows: Copy Code code as follows: [Root@krlcgcms01 mytest]# SH fun.sh

When writing a shell script, we need to use a variety of special symbols, through these special symbols can make us write code more concise and efficient, here to the summary: 1, {} curly braces:Usage One: Wildcard extensionEg:ls My_{finger,toe}sThis command corresponds to a combination of the following commands:LS my_fingers my_toesEg:mkdir {Usera,userb,userc}-{home,bin,data}We will get Usera-home, Usera-bin, Usera-data, Userb-home, Userb-bin,userb-

SHC can be used to encrypt shell scripts, which can be converted into an executable binary file. After SHC the shell script, it generates two new files at the same time, one is the encrypted executable binary (the filename ends with. x), and the other is the original file in C (the filename ends with the. x.c).Here's how to install, SHC, and use examples:Download installation:(Website download address: http

Today on the Internet to see a web connection average time of the shell command, in their own machine tried, found that can not use, incredibly appear awk:fatal:division by zero attempted such a mistake, Mao's own changed the shell command. Original Shell Script Example: Copy Code code as follows: Cat access.log|grep "Connect CBP" |awk ' begin{s

example, we all cut according to line 1000.[Email protected] test]# split-l a.txt[Email protected] test]# Wc-l *XaaXabXacThis way, each file is 1000 rows. After the target file, you can directly empty the contents.[Email protected] ~]# > A.txt[email protected] ~]# cat A.txt Annotation characters#: The shell entered after the # number does not come back into effect, and its role is to explain the explanation.$: variable prefix,! $ combin

1. Basic Knowledge1.1 What is Shell programming?In Unix, shell is not a simple command interpreter (typical DOS in Windows), but a fully functional programming environment. Shell is a part of the operating system, used to deal with users, and can be used to coordinate various commands [1 ]. It is very convenient to use Shell