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/prof...
基本语法: case$variableinpattern1)# commands to be executed if $variable matches pattern1;; pattern2)# commands to be executed if $variable matches pattern2;; *)# commands to be executed if $variable doesn't match any pattern;;esac 示例: #!/bin/bashday="Monday"case$dayinMonday)echo"To...
gcp_ansible_create_credential.sh - creates an Ansible service account with permissions on the current project, creates and downloads a credential key json and prints the environment variable to immediately use it gcp_cli_create_credential.sh - creates a GCloud SDK CLI service account with full ow...
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 ${parameter:+word} to ensure that ...
a.txt does not exist 从上面的示例中不难看出,&&的作用是,如果上一步命令返回状态为0(成功)则继续执行后面的命令,否则终止执行;||的作用刚好反过来,如果上一步命令返回状态为非0(失败),则继续执行下去。这种用法有时又叫做“短路”,因为后一步命令是否会执行,依赖于前一步命令的执行结果。我们再举一个更绕...
If it does not exist, EOF signifies the end of input to the shell. INPUTRC The filename for the readline startup file, overriding the default of ~/.inputrc (see READLINE below). LANG Used to determine the locale category for any category not specifically selected with a variable starting ...
If you want to detect bash-preexec in your library (for example, to add hooks topreexec_functionswhen available), use the Bash variablebash_preexec_imported: if[[-n"${bash_preexec_imported:-}"]];thenecho"Bash-preexec is loaded."fi ...
read [-options] [variable...]上面语法中,options是参数选项,variable是用来保存输入数值的一个或多个变量名。如果没有提供变量名,环境变量REPLY会包含用户输入的一整行数据。下面是一个例子demo.sh。#!/bin/bash echo -n "输入一些文本 > " read text echo "你的输入:$text"上面例子中,先显示一行提示文本...
set means VARIABLE is non-empty (VARIABLE="something") empty means VARIABLE is empty/null (VARIABLE="") unset means VARIABLE does not exist (unset VARIABLE) Values: $VARIABLE means the result is the original value of the variable. "default" means the result was the replacement string provide...
登录后复制case"variable"in"pattern1")Command… ;;"pattern2")Command… ;;"pattern2")Command… ;; esac 注意: 条件语句最后总会包含一个空格和右括号 ); 条件语句后的命令以两个分号 ;; 结束,其前面的空格可有可没有; case 语句 以 esac 结尾(与 case 相反)。