[ken ~]$lsnon_exist ||touchnon_exist &&echofile non_exist created non_exist file non_exist created 因为non_exist文件不存在,ls命令返回了失败。紧接着是||,所以会继续执行第二步——创建该文件。再接下来是&&,因为上一步创建命令成功,所以继续执行并打印file non_exist created。 第二个命令,这时候文...
/bin/bashecho${var:-"Variable is not set"} ---> Variable is not setecho"1 - Value of var is ${var}" ---> 1- Value of var isecho${var:="Variable is not set"} --->Variable is not set 同时var已经被赋值为Variable is not setecho"2 - Value of var is ${var}" --->2 -...
登录后复制#!/bin/bashif[$#-ne 1 ];thenecho"Error: Invalid number of arguments"exit1fifile=$1if[ -f$file];thenecho"$fileis a regular file."elif[ -L$file];thenecho"$fileis a soft link."elif[ -d$file];thenecho"$fileis a directory."elseecho"$filedoes not exist"fi 在脚本的开...
但是在接下来的步骤中,我希望生成一个变量名,并检查具有变量名的变量是否存在,如下面所示。echo "VARIABLE does not exist" echo "VARIABLE exist"然而,这是行不通的</ 浏览5提问于2016-08-20得票数 0 回答已采纳 2回答 在bash中,只有变量的if语句会计算到什么? 、、 我正在学习bash --登录,并看到/etc/...
/bin/bashfile="example.txt"if[ -e$file];thenecho"File exists."elseecho"File does not exist."fi 在这个示例中,脚本检查example.txt文件是否存在。 6. 组合条件 在Bash 中,可以使用逻辑运算符组合多个条件: 逻辑与:-a或&& 逻辑或:-o或||
Though be careful if your shell script runs with the set -u option and your variable does not exist, then your script will fail with an error like bash: myVar: unbound variable. To work around this, you can test with a parameter expansion by using ${parameter:+word} to ensure that ...
If it does not exist, EOF signifies the end of input to the shell. INPUTRC The filename for the readline startup file, overriding the default of ~/.inputrc (see READLINE below). LANG Used to determine the locale category for any category not specifically selected with a variable starting ...
Each time it is invoked, getopts places the next option in the shell variablename, initializingnameif it does not exist, and the index of the next argument to be processed into the variableOPTIND. OPTINDis initialized to 1 each time the shell or a shell script is invoked. ...
forvariableinlistdocommandsdone 上面语法中,for循环会依次从list列表中取出一项,作为变量variable,然后在循环体中进行处理。 关键词do可以跟for写在同一行,两者使用分号分隔。 forvariableinlist;docommandsdone 下面是一个例子。 #!/bin/bashforiinword1 word2 word3;doecho$idone ...
echo"$FILE is executable/searchable."fielseecho"$FILE does not exist"fi 这个例子中就有大量的Test。 case case其实就是我们熟悉的那个swich,但语法形式上有很大的不同。 代码语言:javascript 代码运行次数:0 运行 AI代码解释 case"$variable"in"$condition1")command...;;"$condition2")command...;;esac...