Shell

Shell arithmetic operation addition Note! ' 4 ' + ' 5 ' between these three should have blank r= ' expr 4 + 5 ' echo $rr =$[4 + 5]echo $rr =$ ((4 + 5)) echo $r multiplication r= ' expr 4 \* 5 ' r=$ ((4 * 5)) r=$[4 * 5]echo $r Division r= ' Expr 40/5

LS-LH //view file sizeLS-LH filename //View the actual size of a filedu-h //Viewing the size of a file as a diskdu-h filename //View the size of a fileThat LS looks at the actual size of the file, Du is looking at the size of the disk blockDu

Creation and execution of a script1. Create file *.sh, file suffix sh2. Editing scriptsThe first line must be: #!/bin/bash #指定解释脚本的shell3. Empoweringchmod u+x a.sh4. Implementation./a.shVariables in the two shell scripts1. Definition and deletion of

Batch modify file suffixThe first type:#!/bin/bashfor fn in *.$1domv $fn ${fn%$1}$2doneThe second type:Find. -name "*.txt" | Awk-f ' [./]+ ' {print $} ' | Xargs-i-T mv {}.txt {}.shGREP User TipsThe file is as follows:# cat Test.txt This was a test

The code is as follows:#ac = ' ifconfig -a | grep encap | awk  ' {print $1} ' ac= ' ifconfig |  grep encap | awk  ' {print $1} ' for i in  $acdo          if [  $i  ==  "Lo"  ];then         echo  $i         ifconfig  $i  |  grep  "inet addr"  | sed  '

The most recent thing about egg aches is that you need to get root in the shell script, so you need to enter a password when the shell script is running.Lazy I certainly want to let the shell in the execution process can automatically enter the

Implementation requirements: Create user student1 to Student50, specify Group as student group! And each user needs to set a different password! The script is implemented as follows:#!/bin/bashfor i in ' seq 1 "do useradd-g student student$i; echo

Variable settings:~/dos # dfs=2 Variable use:You can read it using EHCO, but you need to precede the variable name with $, or the ${variable}.~/dos # echo $dfs 2 ~/dos # echo ${dfs}

#批量修改当前目录下的文件扩展名, change. doc to. txt1. [email protected] rendir]# vim. /renfilex.sh2. #!/bin/bash3. For FILE in "$"4. Do5. mv $FILE ${file%$1} "$"6. Done++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++Write a

[[email protected] ~]# mkdir shell[[email protected] ~]# cd shell/[[ email protected] shell]# vim first.sh#!/bin/bash                                 must be # #the  first test shell script.             Description # #written  by guozhen.mkdir 123   

For tired print and Echo, try a little bit of fresh effort.1. Using the shell's execution optionsThe common execution directives for SH and bash are:-N,-X,-C,-V.which-N is a shorthand for noexec, which is to do only the syntax checking of the script

SSH Main parameter description-L Specify Login user-P Set Port number-F run in the background, and recommended with the-n parameter-n redirects standard input to/dev/null to prevent reading standard input-N Do not execute remote command, only port

When you create a child process with fork (), you execute the same program as the parent process (but it is possible to execute a different code branch), and the child process often calls one of the exec functions to execute another program.Process

Some knowledge of variables in the shell:Variable:1. By default, all variables are considered to be stored as strings.2. Variable case sensitivity3. Add $ to the variable name before accessing the content4. No declaration required5. The $ extension

The structural characteristics of the all-back text are as follows:Assuming that the number of characters is even, it is structurally represented as a sequence of characters with the same character but with the opposite sequence of

* Wildcard character (* for 0 or more arbitrary characters)[[email protected] ~]# ls *.txtA.txt1. txt:2. txt:？ Represents only one arbitrary character[email protected] ~]# Touch Testa[[email protected] ~]# touch Testb.txt[[email protected] ~]# ls-d

1. Check if the remote port is open for bash: echo >/dev/tcp/8.8.8.8/53 && echo "open" 2. Turn the process into the background: Ctrl + z 3. Transfer the process to the foreground: fg 4. Generates a random

There's nothing going on today. A lot of operations in the shell about efficiency issuesNo, nothing else, no use.It's just something to do.At first, that's the arithmetic.What I recommend here is to use the $ (()) method for simple

#include #include #include using namespace std;void swap (int a[], int i, int j); void Insert_sort (int a[], int n) {for (int i = 1; i =inc&&temp 0; i--) {for (int j = 1; j i; j--) {if (A[j] = r) {return;} int middle = (L + R)/2;merge_sort (A, L,

This note is for the early ximo of the shelling Basic video tutorial, organized notes. the tools used in this note:http://download.csdn.net/detail/obuyiseng/9466056Exe32pack1.ESP Law1, the program loaded into the OD, found that there is a large