by the `test'builtin, and may be combined using the following operators:( EXPRESSION ) Returns the value of EXPRESSION! EXPRESSION TrueifEXPRESSION isfalse;elsefalseEXPR1&& EXPR2 Trueifboth EXPR1 and EXPR2 aretrue;elsefalseEXPR1|| EXPR2 Trueifeither EXPR1 or EXPR2 istrue;elsefalseWhen the...
B-2. TEST Operators: Binary ComparisonB-3. TEST Operators: FilesB-4. Parameter Substitution and ExpansionB-5. String OperationsB-6. Miscellaneous ConstructsC-1. Basic sed operatorsC-2. Examples of sed operatorsD-1. "Reserved" Exit CodesL-1. Batch file keywords / variables / operators, and...
Whenthe ‘==’and‘!=’ operatorsareused, the stringtotherightofthe operatorisconsidered apatternandmatched accordingtothe rules described belowinPatternMatching,asif the extglob shell option were enabled. The ‘=’ operatorisidenticalto‘==’. If the nocasematch shell option (see the description...
by the `test'builtin, and may be combined using the following operators:( EXPRESSION ) Returns the value of EXPRESSION! EXPRESSION TrueifEXPRESSION isfalse;elsefalseEXPR1&& EXPR2 Trueifboth EXPR1 and EXPR2 aretrue;elsefalseEXPR1|| EXPR2 Trueifeither EXPR1 or EXPR2 istrue;elsefalseWhen the...
You can modify the value of a variable using arithmetic operators by using theletcommand: letchapter_number=$chapter_number+1echo$chapter_number ## 6 You can also store strings in variables: the_empire_state="New York"echo$the_empire_state ...
Shellvariables are allowedasoperands.Thename of the variable isreplacedbyits value(coerced to afixed-width integer)within an expression.Thevariable neednothave its integer attribute turned on to be usedinan expression. ###shell变量被允许作为操作数。在一个表达式里,变量的名字被替换为它的值。 Operat...
In this example, we have two variables, ‘a’ and ‘b’. The script checks if ‘a’ is equal to ‘b’. If it’s not, it moves on to the ‘elif’ statement to check if ‘a’ is greater than ‘b’. If neither condition is met, it executes the ‘else’ statement, which in ...
1对于Bash,有三种基本的标记(称为token),它们分别是:reserved words(保留字), words, and operators(运算符),reserved words一般是对于shell有特色意义的保留词,比如控制流程语句中的if和while,operators包括比如|或者>等 2.Bash中的元字符 Bash中的元字符是一些有着特殊含意的字符, 在Bash的解释中不是按照字面含意...
It is recommended to quote variables, especially when they contain spaces or special characters to avoid unwanted escaping by the shell, on expansion.2. Shorthand version of test commandIt is not necessary to use the test keyword if you want to run the test command. We can also enclose the...
Define two numbers:The script initializes two variables,num1andnum2, with values5and10, respectively. Compare the numbers:Theifstatement uses the-leoperator to check if the value ofnum1is less than or equal tonum2. Execute the true condition:If the condition evaluates to true (the first nu...