通用自定义
我在这样的 bash 脚本中提示问题：
optionsAudits=("Yep" "Nope")
echo "Include audits?"
select opt in "${optionsAudits[@]}"; do
case $REPLY in
1) includeAudits=true; break ;;
2) includeAudits=false; break ;;
"n") echo "You pressed enter"; break ;; # <--- doesn't work
*) echo "What's that?"; exit;;
esac
done
按下回车键时如何选择默认选项？"n"案例无法捕获回车键。
为了补充 Aserre 的有用答案，该答案解释了代码的问题并提供有效的解决方法，其中包含背景信息和允许空输入的通用、可重用的自定义select实现：
>背景资料明确说明：select本身忽略空输入(只需按Enter键)并简单地重新提示- 用户代码甚至无法运行响应。
实际上，select使用空字符串向用户代码发出信号，表明键入了无效的选项.
也就是说，如果输出变量 -$opt，在本例中为 int - 在select语句中为空，则意味着用户键入了无效的选择索引。
输出变量接收所选选项的文本(在本例中为'Yep'或'Nope')，而不是用户键入的索引。
(相比之下，代码检查的是$REPLY而不是输出变量，输出变量准确包含用户键入的内容，在有效选择的情况下，这是索引，但可能包含额外的前导和尾随空格)。
请注意，如果您不想允许空输入，您可以只需在提示文本中向用户指示可以使用^C(Ctrl+C) 中止提示。
通用自定义select函数，也接受空输入
以下函数密切模拟select的功能，同时还允许空输入(只需按Enter键)。请注意，该函数会截获无效输入，打印警告，然后重新提示：
# Custom `select` implementation that allows *empty* input.
# Pass the choices as individual arguments.
# Output is the chosen item, or "", if the user just pressed ENTER.
# Example:
# choice=$(selectWithDefault 'one' 'two' 'three')
selectWithDefault() {
local item i=0 numItems=$#
# Print numbered menu items, based on the arguments passed.
for item; do # Short for: for item in "$@"; do
printf '%sn' "$((++i))) $item"
done >&2 # Print to stderr, as `select` does.
# Prompt the user for the index of the desired item.
while :; do
printf %s "${PS3-#? }" >&2 # Print the prompt string to stderr, as `select` does.
read -r index
# Make sure that the input is either empty or that a valid index was entered.
[[ -z $index ]] && break # empty input
(( index >= 1 && index <= numItems )) 2>/dev/null || { echo "Invalid selection. Please try again." >&2; continue; }
break
done
# Output the selected item, if any.
[[ -n $index ]] && printf %s "${@: index:1}"
}
您可以按如下方式调用它：
# Print the prompt message and call the custom select function.
echo "Include audits (default is 'Nope')?"
optionsAudits=('Yep' 'Nope')
opt=$(selectWithDefault "${optionsAudits[@]}")
# Process the selected item.
case $opt in
'Yep') includeAudits=true; ;;
''|'Nope') includeAudits=false; ;; # $opt is '' if the user just pressed ENTER
esac
让函数本身处理默认逻辑的替代实现：谢谢，RL-S
此实现在两个方面与上述实现不同：
它允许您在选项中指定默认值，方法是在它前面加上
!，否则第一个选项将成为默认值。默认选项打印时带有尾随[default](并且不带前导!)。然后，该函数将空输入转换为默认选项。所选选项将作为基于
1的索引而不是文本返回。换句话说：您可以假设在函数返回时做出了有效的选择，并且该选择由其在给定选项中的位置指示。
# Custom `select` implementation with support for a default choice
# that the user can make by pressing just ENTER.
# Pass the choices as individual arguments; e.g. `selectWithDefault Yes No``
# The first choice is the default choice, unless you designate
# one of the choices as the default with a leading '!', e.g.
# `selectWithDefault Yes !No`
# The default choice is printed with a trailing ' [default]'
# Output is the 1-based *index* of the selected choice, as shown
# in the UI.
# Example:
# choice=$(selectWithDefault 'Yes|No|!Abort' )
selectWithDefault() {
local item i=0 numItems=$# defaultIndex=0
# Print numbered menu items, based on the arguments passed.
for item; do # Short for: for item in "$@"; do
[[ "$item" == !* ]] && defaultIndex=$(( $i + 1)) && item="${item:1} [default]"
printf '%sn' "$((++i))) $item"
done >&2 # Print to stderr, as `select` does.
# Prompt the user for the index of the desired item.
while :; do
printf %s "${PS3-#? }" >&2 # Print the prompt string to stderr, as `select` does.
read -r index
# Make sure that the input is either empty or that a valid index was entered.
[[ -z $index ]] && index=$defaultIndex && break # empty input == default choice
(( index >= 1 && index <= numItems )) 2>/dev/null || { echo "Invalid selection. Please try again." >&2; continue; }
break
done
# Output the selected *index* (1-based).
printf $index
}
示例调用：
# Print the prompt message and call the custom select function,
# designating 'Abort' as the default choice.
echo "Include audits?"
ndx=$(selectWithDefault 'Yes' 'No', '!Abort')
case $ndx in
1) echo "include";;
2) echo "don't include";;
3) echo "abort";;
esac
可选阅读：原始代码的更惯用版本
注意：此代码不能解决问题，但显示了select语句的更多惯用用法;与原始代码不同，如果做出无效选择，此代码会重新显示提示：
optionsAudits=("Yep" "Nope")
echo "Include audits (^C to abort)?"
select opt in "${optionsAudits[@]}"; do
# $opt being empty signals invalid input.
[[ -n $opt ]] || { echo "What's that? Please try again." >&2; continue; }
break # a valid choice was made, exit the prompt.
done
case $opt in # $opt now contains the *text* of the chosen option
'Yep')
includeAudits=true
;;
'Nope') # could be just `*` in this case.
includeAudits=false
;;
esac
注意：
case语句已移出select语句，因为后者现在保证只能进行有效的输入。case语句测试输出变量($opt)而不是原始用户输入($REPLY)，该变量包含选择文本，而不是其索引。
您的问题是由于select将忽略空输入。对于您的情况，read将更合适，但您将失去select自动菜单创建提供的实用程序。
为了模仿select的行为，你可以做这样的事情：
#!/bin/bash
optionsAudits=("Yep" "Nope")
while : #infinite loop. be sure to break out of it when a valid choice is made
do
i=1
echo "Include Audits?"
#we recreate manually the menu here
for o in "${optionsAudits[@]}"; do
echo "$i) $o"
let i++
done
read reply
#the user can either type the option number or copy the option text
case $reply in
"1"|"${optionsAudits[0]}") includeAudits=true; break;;
"2"|"${optionsAudits[1]}") includeAudits=false; break;;
"") echo "empty"; break;;
*) echo "Invalid choice. Please choose an existing option number.";;
esac
done
echo "choice : "$reply""
更新的答案：
echo "Include audits? 1) Yep, 2) Nope"
read ans
case $ans in
Yep|1 ) echo "yes"; includeAudits=true; v=1 ;;
Nope|2 ) echo "no"; includeAudits=false; v=2 ;;
"" ) echo "default - yes"; includeAudits=true; v=1 ;;
* ) echo "Whats that?"; exit ;;
esac
这接受"Yep"或"1"或"enter"选择"是"，接受"Nope"或"否""2"，并丢弃其他任何内容。 它还将 v 设置为 1 或 2，具体取决于用户是想要是还是否。
这将满足您的要求。
options=("option 1" "option 2");
while :
do
echo "Select your option:"
i=1;
for opt in "${options[@]}"; do
echo "$i) $opt";
let i++;
done
read reply
case $reply in
"1"|"${options[0]}"|"")
doSomething1();
break;;
"2"|"${options[1]}")
doSomething2();
break;;
*)
echo "Invalid choice. Please choose 1 or 2";;
esac
done
假设您的默认选项是Yep：
#!/bin/bash
optionsAudits=("Yep" "Nope")
while : #infinite loop. be sure to break out of it when a valid choice is made
do
i=1
echo "Include Audits?: "
#we recreate manually the menu here
for o in "${optionsAudits[@]}"; do
echo " $i) $o"
let i++
done
read -rp "Audit option: " -iYep
#the user can either type the option number or copy the option text
case $REPLY in
"1"|"${optionsAudits[0]}") includeAudits=true; break;;
"2"|"${optionsAudits[1]}") includeAudits=false; break;;
"") includeAudits=true; break;;
*) echo "Invalid choice. Please choose an existing option number.";;
esac
done
echo "choice : "$REPLY""
echo "includeAudits : "$includeAudits""
注意到这行：
read -rp "Audit option: " -eiYep
我也拉起$reply来$REPLY，以便案件判决更好地工作。
现在，按 Enter 后，输出将如下所示：
Include Audits?:
1) Yep
2) Nope
Audit option: Yep
choice : ""
includeAudits : "true"
#
作为对select的增强，read -eiYep将预先向输入缓冲区提供Yep默认值。
使用默认值的唯一缺点是必须按几次退格键才能输入自己的答案。