tered, an attemptismadetodefine afunctionusing``-f foo=bar'', an attempt is made to assign avaluetoareadonlyvariable, an attemptismadetoassign a valuetoan array variable withoutusingthe compound assignment syntax (see Arrays above), oneofthe namesisnota valid shell variable name, an attempti...
/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 ${var}" --->2 -...
上面那种常规方法,写法比较麻烦,所以set -e 参数解决了这一烦恼 #!/usr/bash set -e var echo "hello world" 执行上面脚本,结果如下 test: line 5: var: command not found set +e 取消 #!/usr/bash set -e set +e var echo "hello world" 执行上面脚本,结果如下 test: line 5: var: command ...
在bash中,可以使用间接引用(indirect reference)来引用另一个变量中的变量。间接引用是通过使用变量的名称作为另一个变量的值来实现的。 具体而言,可以使用`${!variable}...
EN首先启动终端。 单击屏幕左上角的Ubuntu图标，在弹出的窗口中点击搜索栏，输入“terminal”， 稍等...
set -x echo "today is :"$(date +'%Y-%m-%d') set +x echo "end..." 修改之后的脚本加入了PS4变量, 它是调试信息的前缀,默认值是"+", 我们可以修改它的值,达到输出的调试信息中包含行号的目的 上述代码中 "${BASH_SOURCE}" 表示 当前执行的shell脚本的相对路径,在这里用来表示脚本文件名,"${LIN...
command, not just those that precede thecommandname.-mJob control is enabled.-nRead commands butdonot execute them.-ooption-name Set the variable corresponding to option-name: allexport same as-abraceexpand same as-Bemacs use an emacs-style line editing interface ...
./run: line 3: foo: command not found bar 可以看到输出了错误信息,并继续执行。 如果我们想保证单行如果出现错误,就中断执行脚本,可以有三种写法: # 方法一 command || exit 1 # 方法二 if ! command; then exit 1; fi # 方法三 command
ShellCheck will warn when using features not supported by the shebang. For example, if you set the shebang to#!/bin/sh, ShellCheck will warn about portability issues similar tocheckbashisms: echo{1..$n}# Works in ksh, but not bash/dash/shecho{1..10}# Works in ksh and bash, but ...
if [[ ! -v var ]]; then echo "Variable is not set" elif [[ -z "$var" ]]; then echo "Variable is set to the empty string" else echo "Variable has the value: $var" fi OUTPUT 1 2 3 Variable has the value: /root Use the if-else statement with the -n option to check...