我正在Ubuntu系统上工作，目前我正在做的是:
if ! which command > /dev/null; then
echo -e "Command not found! Install? (y/n) \c"
read
if "$REPLY" = "y"; then
sudo apt-get install command
fi
fi
大多数人都会这么做吗?还是有更优雅的解决方案?
当前回答
这个就行了。Apt-get install是幂等的。
sudo apt-get install --no-upgrade command
其他回答
有点以你的为基础，只是更“优雅”一点。只是因为我很无聊。
#!/bin/bash
FOUND=("\033[38;5;10m")
NOTFOUND=("\033[38;5;9m")
PKG="${@:1}"
command ${PKG} &>/dev/null
if [[ $? != 0 ]]; then
echo -e "${NOTFOUND}[!] ${PKG} not found [!]"
echo -e "${NOTFOUND}[!] Would you like to install ${PKG} now ? [!]"
read -p "[Y/N] >$ " ANSWER
if [[ ${ANSWER} == [yY] || ${ANSWER} == [yY][eE][sS] ]]; then
if grep -q "bian" /etc/os-release; then
sudo apt-get install ${PKG}
elif grep -q "arch" /etc/os-release; then
if [[ -f /bin/yay ]] || [[ -f /bin/yaourt ]]; then
yaourt -S ${PKG} 2>./err || yay -S ${PKG} 2>./err
else
sudo pacman -S ${PKG}
fi
elif grep -q "fedora" /etc/os-release; then
sudo dnf install ${PKG}
else
echo -e "${NOTFOUND}[!] This script couldn't detect your package manager [!]"
echo -e "${NOTFOUND}[!] Manually install it [!]"
fi
elif [[ ${ANSWER} == [nN] || ${ANSWER} == [nN][oO] ]]; then
echo -e "${NOTFOUND}[!] Exiting [!]"
fi
else
echo -e "${FOUND}[+] ${PKG} found [+]"
fi
apt list [packagename]
这似乎是在DPKG和旧apt-*工具之外最简单的方法。
这个命令是最容易记住的:
dpkg --get-selections <package-name>
如果已经安装，它会打印:
<包名称>安装
否则它会打印
没有找到匹配<package-name>的包。
这是在Ubuntu 12.04.1 (Precise穿山甲)上测试的。
如果您的包具有命令行接口，则可以在安装之前通过调用它的命令行工具来计算输出，从而检查包是否存在。
这里有一个叫做helm的包的例子。
#!/bin/bash
# Call the command for the package silently
helm > /dev/null
# Get the exit code of the last command
command_exit_code="$(echo $?)"
# Run installation if exit code is not equal to 0
if [ "$command_exit_code" -ne "0" ]; then
# Package does not exist: Do the package installation
else
echo "Skipping 'helm' installation: Package already exists"
fi;
我根据Nultyi的回答选择了一个:
MISSING=$(dpkg --get-selections $PACKAGES 2>&1 | grep -v 'install$' | awk '{ print $6 }')
# Optional check here to skip bothering with apt-get if $MISSING is empty
sudo apt-get install $MISSING
基本上，来自dpkg——get-selections的错误消息比其他大多数错误消息更容易解析，因为它不包括“deinstall”这样的状态。它还可以同时检查多个包，这是仅使用错误代码无法做到的。
解释/例子:
$ dpkg --get-selections python3-venv python3-dev screen build-essential jq
dpkg: no packages found matching python3-venv
dpkg: no packages found matching python3-dev
screen install
build-essential install
dpkg: no packages found matching jq
因此grep从列表中删除已安装的包，awk从错误消息中提取包名，导致MISSING='python3-venv python3-dev jq'，它可以简单地插入到安装命令中。
我不是盲目地发布apt-get install $PACKAGES，因为正如评论中提到的，这可能会意外地升级你没有计划的包;对于期望稳定的自动化流程来说，这并不是一个好主意。
