if test –d ~/tmp then echo “the directory already exists” else mkdir ~/tmp fi 试说明该代码段主要实现了什么功能?相关知识点: 试题来源: 解析 答:该代码段主要实现的功能为:判断用户主目录下的子目录tmp是否存在,并根据判断结果做出如下处理: 存在: 显示“the directory already exists” 不存在: 建立...
- Test if the specified variable has a [n]on-empty value: [[ -n $variable ]] - Test if the specified variable has an empty value: [[ -z $variable ]] - Test if the specified [f]ile exists: [[ -f path/to/file ]] - Test if the specified [d]irectory exists: [[ -d path/...
21. Test if File Exists In order to check if a given file exists, users can perform conditional tests. In this case, we’ll useanifstatement with a-fflag. The flag checks if a given file exists and is a regular file. Start by creating the script file: nano exists.sh Copy and past...
We are checking if the given file exists or not. Since there is the negation (!) operator and as the directory doesn’t exist, it will execute the then block of the code. This will enable the touch command to execute which will create the file. If we don't want the modification time...
For example, to test if the file/tmp/test.logexists, run the following command: test -f /tmp/test.txt The first line executes the test to see if the file exists. The second command,echo, displays the results. The result0means that the file exists, while1means no file was found. ...
-x:Executable...可执行 ... 条件判断的表达式: [ expression ] 注意[] 最左和左右需要空格,这里linux把表达式当成命令来判断 ` expression ` 同样需要注意空格,这里linux把表达式当成关键字来判断,至于两者区别,暂时存疑 test expression 命令间的逻辑
[ -s FILE ] True if FILE exists and not empty (size more than 0). [ -r FILE ] True if FILE exists and is readable. [ -w FILE ] True if FILE exists and is writable. [ -x FILE ] True if FILE exists and is executable. [ -L FILE ] True if FILE exists and is symbolic lin...
This checks whether a file is executable (by the current user) or not. If a file is executable, then it returns 0, else it returns 1: [ test -x filename ] && echo executable || echo non-executable You can use other file permissions like r and w in the same fashion. Other common...
-x file exists and is executable by the current process. -z string length is zero. 字符测试:字符串比较 双目: >: 大于则为真 <: 小于则为真 >=:大于等于则为真 <=:小于等于则为真 ==:等于则为真 !=:不等于则为真 单目: -n String: 是否不空,不空则为真,空则为假 ...
/bin/bash# Check if the file "abc.sh" existsif[-e"abc.sh"];then# Check if the file is executableif[-x"abc.sh"];then# If executable, run the script./abc.shelse# If not executable, print messageecho"Script is not executable"fielse# If the file does not exist, print messageecho...