When creating a Bash variable, it must have a value. However, we can use some tricks to set a default value if the variable is not set (ornull). This guide will demonstrate how to do just that. Default shell variable values Method 1 – Setting variable value (if unset) Let’s get ...
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 ...
/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 -...
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 errexit same as-eerrtrace sam...
if [ $gender = femal ]; then---right. if [ $gender= femal ]; then---wrong. if [ $gender=femal ]; then---wrong. 4 如果if 和 then写在同一行, 那么,注意, then的前面要跟上 ; 号. 如果then 换行写, 那么也没问题. eg: if [ $gender = ...
# 取消变量的值 unset my_variable 还可以使用环境变量为变量赋值。例如,可以使用$PATH环境变量: 代码语言:txt 复制 # 使用环境变量为变量赋值 current_path=$PATH echo "当前的PATH环境变量值为:$current_path" 参考链接: Bash变量赋值 相关搜索: linux bash 变量赋值 在bash中赋值位置变量 如何为bash中的布尔值...
在Bash脚本中 set -e 是什么意思 我正在研究这个预安装(preinst)脚本的内容,该脚本会在从Debian软件包(.deb)文件解压该包之前执行。 #!/bin/bashset-e # Automatically added by dh_installinitif["$1"=install];thenif[-d/usr/share/MyApplicationName];then...
# set variable identifying the chroot you work in (used in the prompt below) if [ -z "${debian_chroot:-}" ] && [ -r /etc/debian_chroot ]; then debian_chroot=$(cat /etc/debian_chroot) fi # set a fancy prompt (non-color, unless we know we "want" color) ...
ShellCheck will warn when using features not supported by the shebang. For example, if you set the shebang to#!/bin/sh, ShellCheck will warn about portability issues similar tocheckbashisms: echo{1..$n}# Works in ksh, but not bash/dash/shecho{1..10}# Works in ksh and bash, but ...
is a ! or a ^ then any character not enclosed is matched. The sorting order of characters in range expressions is determined by the current locale and the value of the LC_COLLATE shell variable, if set. A - may be matched by including it as the first or last character in the set. ...