-w file检测文件是否可写，如果是，则返回 true。[ -w $file ] 返回 true。-x file检测文件是否可...
[ FILE1 -nt FILE2 ] 如果 FILE1 has been changed more recently than FILE2, or 如果 FILE1 exists and FILE2 does not则为真。 [ FILE1 -ot FILE2 ] 如果 FILE1 比 FILE2 要老, 或者 FILE2 存在且 FILE1 不存在则为真。 [ FILE1 -ef FILE2 ] 如果 FILE1 和 FILE2 指向相同的设备和节...
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Shell case in 语句中的*)用来“托底”，万一 expression 没有匹配到任何一个模式，*)部分可以做一些...
When you are working on a shell script inbash, there are cases where you want to check if a particular file exists (or does not exist) in a directory, and then perform an action based on the condition. Inbash, there are several ways to check whether or not a file exists inbash. In...
file=”/etc/passwd” if [ -e $file ] then echo “$file exists.” else echo “$file does not exist.” fi “` 五、多条件判断 在实际编程中,我们可能需要同时判断多个条件,可以使用逻辑运算符进行组合。以下代码演示了如何使用逻辑与(&&)、逻辑或(||),以及逻辑非(!)进行多条件判断: ...
for变量名in取值列表do命令 done 语法二: for ((expr1;expr2;expr3));do 命令列表 done 实例: #提前准备好用户的文件[root@VM_0_10_centos shellScript]#vi username.txttest01 test02 test03 test04 test05 test06#vi example.sh#!/bin/bashread -p"请输入用户密码:"PASSWDforUNAMEin`cat username....
Often when shell scripting with BASH you need to test if a file exists (or doesn’t exist) and take appropriate action. This post looks at how to check if a file exists with the BASH shell. To test if the /tmp/foo.txt file exists, you would do the following, changing the echo lin...
id$UserName&>/dev/null&&useradd$UserName||echo"$UserNameexists."#如果用户存在,则 && 前的部分为假,那么需要判断&& 后面的部分;#如果用户不存在,则 &&前面的部分为真,那么不需要判断&& 后面的部分#对于 || 运算来说,如果用户不存在,则前半部分都为假,则需要运行 || 后面的部分...
echo "The file /etc/fstab exists." else echo "The file /etc/fstab does not exist." fi ``` 在这个例子中,if语句判断/etc/fstab文件是否存在,如果存在则输出一条提示信息,否则输出另一条提示信息。这种条件判断和操作的结构在Shell脚本中应用广泛,帮助用户做出智能决策和自动化执行任务。