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1. String length:Var=123abc456echo ${#var}9expr length $var 92. Specify character interceptionEcho ${var:5} #截取前五个字符c456echo ${var:2:5} #截取第2到第5个字符3abc4echo ${var: 3} 3 characters after intercept (with space on the left) 4563. Interception of

Linux in any case is to use the shell command, in the actual use of the shell, programming experience is very easy to get started, but a little more difficult is the shell inside the symbols, a variety of special symbols when we write the shell

Shellshock analysis CVE-2014-6271 Some time ago, the shell-breaking vulnerabilities made various companies very busy. The vulnerabilities have been around for a while, and the analysis of the Internet has also been transferred. When they stop, it's

PHP empty and empty string differences if Var is a non-null or nonzero value, empty () returns FALSE. In other words, "", 0, "0", NULL, FALSE, Array (), Var $var; and objects that do not have any properties will be considered empty and return TRUE

Difference between PHP isset () and empty (), issetemptyThe isset () function of PHP is generally used to check whether the variable is set.Format: bool isset (mixed var [, mixed var [,...])Function: checks whether variables are set.Return Value:If

PHP's Isset () function is commonly used to detect whether a variable is setFormat: bool Isset (mixed var [, mixed Var [, ...])Function: Detect whether the variable is setreturn value:Returns FALSE if the variable does not existReturns FALSE if the

The isset () function of PHP is generally used to check whether the variable is set.Format: bool isset (mixed var [, mixed var [,...])Function: checks whether variables are set.Return Value:If the variable does not exist, FALSE is returned.If the

The general practice of a large site is to use memory as a database (memcached), and a good read/write splitting backup mechanism (mysql master/slave). in such an environment, how can we develop PHP. Memcache The code is as follows: $ Memcached =

1. in Makefile, Shell scripts can only be called in target, but cannot be output elsewhere. For example, the following code has no output: VAR = & quot; Hello & quot; echo & quot; $ VAR & quot; all: the above code is not output at any time, if the

. Today is the last day in this company. The mood is not good.Therefore, the general practice of a large station is to use memory as a database (Memcached). And a good backup mechanism for read/write separation (mysql Master/Slave)In this

By learning the language of PHP, you should know that it is a function-based HTML scripting language. The large library of functions supports the implementation of PHP language functions. Let's introduce the relevant usage of PHP function isset ()

Summary of PHP static local static variables and Global static variables The reason why static local variables are used is that they cannot be used externally, but their values are retained when they are not used. Although global variables can be

Ec (2); & lt ;? Php returns the last character $ str & quot; JhlIsHero & quot; $ vartrim ($ str); $ lenstrlen ($ var)-1 in PHP; echo $ var {$ len };? & Gt; do PHP and C use a set of continuous addresses to store the last character of a PHP string ...

Empty () only detects variables, and any non-variables will cause parsing errors. In other words, the following statement does not work: empty (addslashes ($ name )) Empty () only detects variables, and any non-variables will cause parsing errors.

The isset () function of PHP is generally used to check whether the variable is set.Format: bool isset (mixed var [, mixed var [,...])Function: checks whether variables are set.Return Value:If the variable does not exist, FALSE is returned.If the

Original: PHP isset () and empty () the use of a different explanationPHP's Isset () function is commonly used to detect whether a variable is setFormat: bool Isset (mixed var [, mixed Var [, ...])Function: Detect whether the variable is setreturn

Parameter filtering1, for parameter bindings that cannot be directly used with PDO, you can use the sprintf simulation and filter using New_addslashes, and then use Query to execute the stitched SQLPercent-return percentage symbol%b-Binary

(1) Definition of an array[Email protected]:~# a= (1 2 3 4)[Email protected]:~# echo ${a[1]}2[Email protected]:~# a[0]=1[Email protected]:~# a[1]=2[Email protected]:~# echo ${a[0]}1(2) Array worth acquiring[Email protected]:~# var[0]=1[Email

Empty () only detects variables, and any non-variables will cause parsing errors. In other words, the following statement does not work: empty (addslashes ($ name )) Empty-check whether a variable is empty Report a bug description Bool empty (mixed

The printf () function is a formatted output function that is typically used to output information to a standard output device in a prescribed format. This function is often used when writing programs. The prototype of the function is: int printf