Rick's Blog bash shell——与if条件相关的参数意义 最近编写脚本,常看到有 if [ -x $variable ] 类的条件语句,不知道相应参数的意义到底是什么, 特摘录如下:fromhttp://blog.csdn.net/aaaaatiger/article/details/1713611 thanks! 1[ -a FILE ] 如果 FILE 存在则为真。2[ -b FILE ] 如果 FILE 存在且...
if grep -q root /etc/passwd; then echo account root exists else echo account root not exist fi if grep -q root /etc/passwd; then echo account root exists else echo account root not exist fi [root@jfht ~]#if grep -q root /etc/passwd; then >echo account root exists >else >echo ...
How to check if a variable exists or is “null”? How to check if a file exists? How to check if a directory exists? How to check if a command succeeds or failed? How to do string comparison and check if a string equals to a value? How to check if a string is in an array?
The pattern will match if it matches any part of the string. Anchor the pattern using the ‘^’ and ‘$’ regular expression operators to force it to match the entire string. The array variable BASH_REMATCH records which parts of the string matched the pattern. The element of BASH_REMATC...
echo "check if variable with name $1 exists"} assert_var "FOO"我们的期望是,应该检测变量FOO,同时也不存在BAR。为此,我需 浏览0提问于2020-07-01得票数 0 回答已采纳 2回答 以未实例化的变量为条件 我是Bash脚本的新手,对C-type语言有更多的经验。我已经编写了一些带有条件的脚本,用于检查未实例化...
if else for 循环 while 语句 until 循环 case 语句 break 命令 continue 命令 函数 参考 Bash(GNU Bourne-Again Shell)是一个为GNU计划编写的Unix shell,它是许多Linux平台默认使用的shell。 shell是一个命令解释器,是介于操作系统内核与用户之间的一个绝缘层。准确地说,它也是能力很强的计算机语言,被称为解释性...
*)# commands to be executed if $variable doesn't match any pattern;;esac 示例: #!/bin/bashday="Monday"case$dayinMonday)echo"Today is Monday.";; Tuesday)echo"Today is Tuesday.";; *)echo"It's some other day.";;esac 在这个示例中,case语句根据变量day的值来决定执行哪个代码块。
TestFile1 exists and is empty. [student@studentvm1 testdir]$ File="TestFile1" ; echo "This is $File" > $File ; if [ -s $File ] ; then echo "$File exists and contains data." ; elif [ -e $File ] ; then echo "$File exists and is empty." ; else echo "$File does not ...
for VARIABLE in file1 file2 file3do command1 on $VARIABLE command2 commandNdone 或 代码语言:javascript 代码运行次数:0 运行 AI代码解释 for OUTPUT in $(Linux-Or-Unix-Command-Here)do command1 on $OUTPUT command2 on $OUTPUT commandNdone 实例 这种for循环的特征是计数。范围由开始(#1)和结束数字...
if [ "$name" == "Alice" ] then echo "Hello, Alice!" else echo "You are not Alice." fi Example 3: File Check #!/bin/bash file_path="/path/to/file.txt" if [ -f "$file_path" ] then echo "File exists." else echo "File does not exist." ...