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bash if、then 和 else 语句

tag-icon • tag-icon bash shell-script scripting
bash if、then 和 else 语句

我正在学习 bash，在尝试编写小脚本时遇到了一个小问题

#!/bin/bash
clear
read num
if [ "$num" -eq 2 ] 

then [ -d "/etc/passwd" ] | sudo cp /etc/passwd /home
        echo -e "${lred}The passwd file has been copied to your home directory. ${NC}"
else 
        echo "The directory does not exist"
fi

我遇到的问题是我想要检查目录，否则在尝试运行复制命令时显示第二个回显“目录不存在”。我得到“cp：无法 stat '/et/passwd'：没有这样的文件或目录”，但第一个回显指出“passwd 文件已复制到您的主目录。”仍然显示，而第二个回显“文件不存在”则不显示。如果有人有解决方案，我真的很感激。谢谢！

编辑：这是我的整个脚本

#!/bin/bash

clear
lred='\033[1;31m'
red='\033[0;31m'
NC='\033[0m' # No Color
blue='\033[0;34m'
lblue='\033[1;34m'

echo -e "${red}Welcome to Lab 7 Utilities Menu ${NC}" # tells echo to enable backslash escapes
sleep 3
clear
echo -e "${lblue}Choose one of the options from the following list:${NC}"
echo -e "${blue}1. Monitor existing processes ${NC}"

echo -e "${blue}2. Copy passwd to /home directory ${NC}"

echo -e "${blue}3. Ping local host ${NC}"

echo -e "${lred}4. Exit ${NC}"

read num 

if [ $num -eq 1 ]

then ps aux
        echo -e "${lred}The list has been successfully generated! ${NC}"
fi

if [ "$num" -eq 2 ]; then
        if [ -e "/etc/passwd" ]; then
           sudo cp /etc/passwd /home
           echo -e "${lred}The passwd file has been copied to your home directory. ${NC}"
        else
           echo "The File does not exist"
        fi
    else
        echo "You entered number that isn't 2"
fi

if [ "$num" -eq 3 ]

then ping -c 4 127.0.0.1
        echo -e "${lred}You have completed pinging localhost. ${NC}"

elif [ "$num" -eq 4 ]

then clear

elif [ "$num" -gt 4 ]
then echo -e "${red}Please choose between number 1 and 4. ${NC}"
clear

fi

答案1

更新（来自我们的聊天），我认为案例陈述更适合您在这里想要完成的任务：

#!/bin/bash

clear
lred='\033[1;31m'
red='\033[0;31m'
NC='\033[0m' # No Color
blue='\033[0;34m'
lblue='\033[1;34m'

# tells echo to enable backslash escapes
echo -e "${red}Welcome to Lab 7 Utilities Menu ${NC}"
sleep 3
clear
echo -e "${lblue}Choose one of the options from the following list:${NC}"
echo -e "${blue}1. Monitor existing processes ${NC}"
echo -e "${blue}2. Copy passwd to /home directory ${NC}"
echo -e "${blue}3. Ping local host ${NC}"
echo -e "${lred}4. Exit ${NC}"

read num

case $num in
        1)
           ps aux
           echo -e "${lred}The list has been successfully generated! ${NC}"
        ;;
        2)
           if [ -e "/etc/passwd" ]; then
              sudo cp /etc/passwd /home
              echo -e "${lred}The passwd file has been copied to your home directory. ${NC}"
           else
              echo "The File does not exist"
           fi
        ;;
        3)
           ping -c 4 127.0.0.1
           echo -e "${lred}You have completed pinging localhost. ${NC}"
        ;;
        4)
           clear
        ;;
        *)
           echo -e "${red}Please choose between number 1 and 4. ${NC}"
        ;;
esac


您确定要将passwd文件复制到该/home目录吗？除此之外，这应该有效：

#!/bin/bash
clear
read num
if [ "$num" -eq 2 ]; then
        if [ -e "/etc/passwd" ]; then
           sudo cp /etc/passwd /home
           echo -e "${lred}The passwd file has been copied to your home directory. ${NC}"
        else
           echo "The File does not exist"
        fi
else
        echo "You entered a number that isn't '2'"
fi

该-d参数检查是否FILE exists and is a directory。你想要的是-e哪个检查FILE exists。

此外，您还尝试|在 后进行管道传输then，这会导致更多冲突，因为它不适合您尝试执行的操作。

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