bash 如何在shell脚本中使用goto语句
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How to use goto statement in shell script
提问by RAHUL.S. KRISHNA
I am beginner in shell script. I don't have any idea about how to use goto statement. I am using the following code.
我是 shell 脚本的初学者。我不知道如何使用 goto 语句。我正在使用以下代码。
start:
echo "Main Menu"
echo "1 for Copy"
echo "2 for exit"
read NUM
case $NUM in
"1")
echo "CopyNUM"
goto start:;
"2")
echo "Haiiii";
goto start:
*)
echo "ssss";
esac
采纳答案by mklement0
As others have noted, there's no gotoin bash(or other POSIX-like shells) - other, more flexible flow-control constructs take its place.
Look for heading Compound Commandsin man bash.
正如其他人所指出的，没有gotoin bash（或其他类似 POSIX 的 shell）——其他更灵活的流控制结构取而代之。
寻找标题Compound Commands在man bash。
In your case, the selectcommand is the right choice.
Since how to use it may not be obvious, here's something to get you started:
在您的情况下，该select命令是正确的选择。由于如何使用它可能并不明显，这里有一些东西可以帮助您入门：
#!/usr/bin/env bash
echo "Main Menu"
# Define the choices to present to the user, which will be
# presented line by line, prefixed by a sequential number
# (E.g., '1) copy', ...)
choices=( 'copy' 'exit' )
# Present the choices.
# The user chooses by entering the *number* before the desired choice.
select choice in "${choices[@]}"; do
# If an invalid number was chosen, $choice will be empty.
# Report an error and prompt again.
[[ -n $choice ]] || { echo "Invalid choice." >&2; continue; }
# Examine the choice.
# Note that it is the choice string itself, not its number
# that is reported in $choice.
case $choice in
copy)
echo "Copying..."
# Set flag here, or call function, ...
;;
exit)
echo "Exiting. "
exit 0
esac
# Getting here means that a valid choice was made,
# so break out of the select statement and continue below,
# if desired.
# Note that without an explicit break (or exit) statement,
# bash will continue to prompt.
break
done
回答by David C. Rankin
Here is a short example using a selectloop to accomplish your goal. You can use a whileloop with a custom menu if you want custom formatting, but the basic menu is what selectwas designed to do:
这是一个使用select循环来实现目标的简短示例。while如果您想要自定义格式，您可以使用带有自定义菜单的循环，但基本菜单的select设计目的是：
#!/bin/bash
## array of menu entries
entries=( "for Copy"
"for exit" )
## set prompt for select menu
PS3='Selection: '
while [ "$menu" != 1 ]; do ## outer loop redraws menu each time
printf "\nMain Menu:\n\n" ## heading for menu
select choice in "${entries[@]}"; do ## select displays choices in array
case "$choice" in ## case responds to choice
"for Copy" )
echo "CopyNUM"
break ## break returns control to outer loop
;;
"for exit" )
echo "Haiiii, exiting"
menu=1 ## variable setting exit condition
break
;;
* )
echo "ssss"
break
;;
esac
done
done
exit 0
Use/Output
使用/输出
$ bash select_menu.sh
Main Menu:
1) for Copy
2) for exit
Selection: 1
CopyNUM
Main Menu:
1) for Copy
2) for exit
Selection: 3
ssss
Main Menu:
1) for Copy
2) for exit
Selection: 2
Haiiii, exiting
