/bin/sha="abc"b="efg"if[ $a =$b ]thenecho"$a = $b : a is equal to b"elseecho"$a = $b: a is not equal to b"fiif[ $a !=$b ]thenecho"$a != $b : a is not equal to b"elseecho"$a != $b: a is equal to b"fiif[ -z $a ]thenecho"-z $a : string length...
-n STRING # True if STRING is not empty STRING1 = STRIN2 # True if strings are equal STRING1 != STRIN2 # True if strings are not equal 算术测试操作 var1 -eq var2 # True if var1 is equal to var2 var1 -ne var2 # True if var1 not equal to var2 var1 -lt var2 # True ...
The last case (#4) is especially naughty because it will execute the command contained in the variable (which is why the condition evaluates to true for valid commands3, 4). Here is a harmless example: var='echo this text will be displayed when the condition is evaluated' if $...
/bin/bash2.# A simple variable example*3. 4.myvariable=Hello 5. 6.anothervar=Fred 7. 8.echo$myvariable$anothervar9.echo10. 11.sampledir=/etc 12. 13. ls$sampledir 运行: user@bash:./simplevariables.sh Hello Fred a2ps.cfg aliases alsa.d ... user@bash: 数组变量: array[0]=valA#...
Returns successifall of the NAMEs are found; failsifany are not found. ###假如所有的NAMEs都找到返回成功;假如任何一个未找到就返回失败。 typeset: typeset [-aAfFilrtux] [-p] name[=value] ... Set variable values and attributes. Obsolete...
STRING1 != STRIN2 # True if strings are not equal 算术测试操作 var1 -eq var2 # True if var1 is equal to var2 var1 -ne var2 # True if var1 not equal to var2 var1 -lt var2 # True if var1 is less than var2 var1 -le var2 # True if var1 is less than or equal to ...
The string is empty Explanation: In the exercise above, The variable 'input_str' is defined as an empty string. An if statement checks if the length of '$input_str' is zero using the -z test operator. If the string is empty, the script prints "The string is empty" using the "echo...
The EXPRESSION is false. -n STRING The length of STRING is greater than zero. -z STRING The lengh of STRING is zero (ie it is empty). STRING1 = STRING2 STRING1 is equal to STRING2 STRING1 != STRING2 STRING1 is not equal to STRING2 INTEGER1 -eq INTEGER2 INTEGER1 is numerically ...
echo "the string is $o" 显示结果重定向至文件:echo "It is a test" > myfile printf printf 命令用于格式化输出, 是 echo 命令的增强版。它是 C 语言 printf() 库函数的一个有限的变形,并且在语法上有些不同。注意:printf 由 POSIX 标准所定义,移植性要比 echo 好。
If true, it prints the current value of i and [increments the variable] i by 1 (i++). Otherwise, the loop terminates. for ((i = 0 ; i <= 1000 ; i++)); do echo "Counter: $i" done The loop will iterate 1001 times and produce the following output: Counter: 0 Counter: 1...