Shell

Condition test1. Test condition tests or [] (test conditions are true false) Example: string comparison#!/bin/bashRead dataTest "$data" = = "Hello" //note there are spaces on either side of the equal sign or [$data = = "Hello"] echo $?

Recently do the computer room bandwidth detection. Recently wrote a shell script to ping the IP of the machine room in bulk, returning the failure rate and the average response time#!/bin/bashlog=$1.logecho-n "" > $logfor i in ' Cat $ do/bin/ping-s 1

The difference between one, ' and $ ()The anti-quote itself escapes the \, retains its own meaning, and if we want to play a special meaning in the anti-quote, we must use 2 \ to represent it. in inverted quotation marks: \ \ = \$ () in: \ = \Note:

The difference between 1, ' and $ ()The anti-quote itself escapes the \, retains its own meaning, and if we want to play a special meaning in the anti-quote, we have to use 2 \ to represent it. So we can simply imagine the inverted quote: \ \ = \$ ()

1. View HelpHadoop fs-help 2. UploadPaths on files > such as: Hadoop fs-put test.log/3. View the contents of the filePaths on Hadoop fs-cat such as: Hadoop fs-cat/test.log4. View File listHadoop Fs-ls/5. Download the filePaths on Hadoop fs-get 6,

What is a shell script?Shell script is similar to batch processing under Windows/dos, that is, the use of various commands pre-placed into a file, convenient one-time execution of a program file, mainly for the convenience of administrator settings

1.Tenth LineHow would you print just the 10th line of a file?For example, assume this file.txt has the following content:Line 1Line 2Line 3Line 4Line 5Line 6Line 7Line 8Line 9Line 10Your script should output the tenth line, which is:Line 10----------

VariableDefining variablesYour_name= "Runoob.com" #变量名和等号之间不能有空格Using variablesYour_name= "QINJX"Echo $your _nameEcho ${your_name}echo "I am good at ${skill}script"echo "I am good at ${skillscript}"Curly braces are added to help the interpreter

The basic meaning of shell variable $#,[email protected],$0,$1,$2 in Linux:Variable Description:$$The PID of the shell itself (ProcessID)$!PID of the Shell's last running background process$?End code of the last Run command (return value)$-Flag at a

Common options for Uniq commandsRemove Duplicate rows-U display non-repeating rows-D shows duplicate rows-C Print the number of repetitions per lineThe test text content is as follows:# Cat 4.txt11111122222222333333334444(1) Uniq# Cat 4.txt | Uniq

1.shell Script InterpreterBourme Shell (/usr/bin/sh or/bin//bin//usr/bin//usr/bin/ for Root (/sbin /SH)Bash is widely used in the development environment because it is easy to use and free2. First shell script#!/bin/"Hello World"#! is a contract tag

Cut command common optionsThe test text content is as follows:# cat Name1.txt name1 alvin1name2 alvin2name3 alvin3name4 alvin4# cat 2.txt name1:100name2:101name3:102(1)-CCut the 1th character of each column# Cat Name1.txt | Cut-c1NNNNCut the 1th, 3-4

The test text content is as follows:# cat Name1.txt name1 alvin1name2 alvin2name3 alvin3name4 alvin4# cat name2.txt name1 100name2 101name3 102CCCCCCCCCCCCCCC C(1) Paste merge each line of two files by one by one# paste Name1.txt name2.txtname1

Reference: http://blog.csdn.net/wanglang3081/article/details/49423105 (1) Makefile is essentially a shell script, that is, each command is a shell process, and the shell process exits when it finishes running. (2) Shell code line, if there is =,

Performance testing, you may change the environment to change, each time the test, the configuration file is different, may cause the test to fail.Suppose there is a correct configuration file for Zoo.cfg.template, and the configuration file for the

Topic linksDp[n] = Sigma (A[i]*dp[n-i]), given a1.....an, Dp[n]. N is 1e5.The form of this equation is obviously a convolution, so you can use the FFT to optimize it, but this will also time out. So you can use the CDQ to optimize the partition.CDQ

First, several commands are elaborated.Echo $ shows the currently used shell versionDpkg-reconfigure Setting the package typeThe reason why the newspaper is wrong:The default shell parsing used by Ubuntu is a feature that Dash,dash only part of

The call file system (FS) shell command should use the form $HADOOP _home/bin/hadoop FS.All FS shell commands use the URI path as the parameter.The URI format is Scheme://authority/path.The scheme for Hdfs,hdfs is HDFs, such as Hdfs://localhost:9000/

First, define variablesDefine variable names without a $ (unlike PHP, as with Python), with no spaces between variable names and "=" (special, unlike other languages)Example: x= "Hello World"Note: The naming of variable names should follow the

Shell scripts are extremely important in operations, and the use of arrays in shell scripts is a very useful aspect in both looping and computing.Here are some operations on the array aspects of the shell script to record here, hoping to help