Shell

[Condition 1-a Condition 2] When 1 and 2 are true [condition 1-o condition 2] when 1 and 2 one is true [! condition] Take counter && and | | 　　Or! unsigned [-D name] && Echo ' is dir ' is true when the name is directory, then the input has the

1. Value Format: Test "NUM1" OPR "num2" ["Num1" OPR "num2"] OPR Value: Equality:-EQ Unequal:-ne

path=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin:/usr/local/mysql/binexport  Java_home=/usr/java  export classpath=.: $JAVA _home/lib/dt.jar: $JAVA _home/lib/tools.jar   export path= $PATH: $JAVA

The program must start with the following line (must be in the first line of the file): #!/bin/shThe symbol #! is used to tell the system that the parameter behind it is the program used to execute the file. In this example we use/BIN/SH to

basic regular expression metacharacters role * matches the previous character 0 or more times . match any character except newline

Shell script (i)1. Common Commands(1) System Management#useradd, a user group with the same user name is created by default when a new user is added#创建用户user1 and specify a UID of 1111, the owning group is 2222 (test), and the home directory is not

If you want to add a character after a variable, you can use the following method: $value 1=home$value2=${value1}"="Echo$value 2 Add the string variable you want to add {}, and you need to put the $ out. The result of this output is: Home=, which

In the shell, especially in the shell loop, some expressions may be used to operateThis requirement can be accomplished using the expr command, such as:x=$ (expr $a + 1)Completed the calculation of the sum of $ A and 1 and assigned the value to

Linux Shell Program DebuggingThe shell program is debugged by adding relevant debugging options when running the program or by adding related statements to the script, allowing the shell program to display some "debug information" for reference

$ who can know how many landings on the system$who |wc-l count the number of usersNote: | is a pipe symbol that can be used to establish a pipeline between two programs (pipeline): The WHO output, a WC input, the result of the WC is the number of

Find DocumentsIt is quite convenient to find text in the grep program (matching text matching). There are traditionally three programs that can be used to find entire text files. grep's oldest text-matching program. The simplest way is to

The shell is an interpretive programming language.The execution of an interpreted script file:When an interpreted script file is executed, the script file is committed to the kernel. The kernel sees the first line of "#! "#! is called when the

For some reason, Xcode has helped me follow the thousands of development and on-line certificates that need to be removed from this part of the certificate:　　#dir="/users/ethan/library/mobiledevice/provisioning

Method Two/sbin/ifconfig-a|grep inet|grep-v 127.0.0.1|grep-v Inet6|awk ' {print $} ' |tr-d ' addr: 'Method OneGet the native IP address and save it in a variablearg=ifconfig eth0 |grep "inet addr"| cut -f 2 -d ":"|cut -f 1 -d " " Ipaddr= a

1.12 Functions and Parameters Like other scripting languages, Bash also supports functions and can pass parameters. 1.12.1 function definition and parameter transfer#!/bin/bash function fname () #也可以用fname () instead of {echo $1 , $

ShellThe shell is a weakly typed programming language.Distinction between strong and weak:Strong: Variables must be declared prior to use, and even require initialWeak: Variables are declared when they are used, even the part is differentiated by

1.8 using Aliases aliases in Linux are the equivalent of shortcuts in Windows, and using aliases can save users from having to enter a long sequence of commands. 1.8.1 Creating temporary aliases (shortcuts)alias new_command=‘command

Defining arraysArr= (1 2 3 4 5)accessing arrays# echo ${arr[0]}1Print all the values in an array# echo ${arr[*]}1 2 3) 4 5Print array length# echo ${#arr [*]}5The above defined array, the index can only be a number, the following will describe the

In Linux, the shell variable $ #, $ @, $0, $1, $2 has the following meanings :, Variable description: $ PID (ProcessID) of Shell itself $! PID of the background Process last run by Shell $? End code of the last command (Return Value) $-Flag list

Shell script to delete the folder N days ago ----- the difference between the date command on linux and mac Background:Every day you build things and put them in different folders by date. For example, today's construction is put in, tomorrow's will