我的Debian服务器设置：

当多个包包含相同的名称时，我遇到了问题。

例如apache2。这就是我的解决方案：

function _apt_install() {
    apt-get install -y $1 > /dev/null
}

function _apt_install_norecommends() {
    apt-get install -y --no-install-recommends $1 > /dev/null
}
function _apt_available() {
    if [ `apt-cache search $1 | grep -o "$1" | uniq | wc -l` = "1" ]; then
        echo "Package is available : $1"
        PACKAGE_INSTALL="1"
    else
        echo "Package $1 is NOT available for install"
        echo  "We can not continue without this package..."
        echo  "Exitting now.."
        exit 0
    fi
}
function _package_install {
    _apt_available $1
    if [ "${PACKAGE_INSTALL}" = "1" ]; then
        if [ "$(dpkg-query -l $1 | tail -n1 | cut -c1-2)" = "ii" ]; then
             echo  "package is already_installed: $1"
        else
            echo  "installing package : $1, please wait.."
            _apt_install $1
            sleep 0.5
        fi
    fi
}

function _package_install_no_recommends {
    _apt_available $1
    if [ "${PACKAGE_INSTALL}" = "1" ]; then
        if [ "$(dpkg-query -l $1 | tail -n1 | cut -c1-2)" = "ii" ]; then
             echo  "package is already_installed: $1"
        else
            echo  "installing package : $1, please wait.."
            _apt_install_norecommends $1
            sleep 0.5
        fi
    fi
}

我同意lhunath不鼓励使用which，他的解决方案对Bash用户完全有效。但是，为了更便于携带，应使用命令-v：

$ command -v foo >/dev/null 2>&1 || { echo "I require foo but it's not installed.  Aborting." >&2; exit 1; }

命令命令符合POSIX。参见此处了解其规范：command-execute一个简单的命令

注意：类型符合POSIX，但类型-P不符合。

我找不到一个可行的解决方案，但编辑了一下后，我想到了这个。这对我有用：

dpkg --get-selections | grep -q linux-headers-$(uname -r)

if [ $? -eq 1 ]; then
        apt-get install linux-headers-$(uname -r)
fi

以下是检查命令是否存在于$PATH中并可执行的便携式方法：

[ -x "$(command -v foo)" ]

例子：

if ! [ -x "$(command -v git)" ]; then
  echo 'Error: git is not installed.' >&2
  exit 1
fi

需要进行可执行检查，因为如果$PATH中找不到具有该名称的可执行文件，bash将返回一个不可执行文件。

还请注意，如果$PATH中存在与可执行文件同名的不可执行文件，则dash会返回前者，即使后者会被执行。这是一个bug，违反了POSIX标准。[错误报告][标准]编辑：从破折号0.5.11（Debian 11）开始，这似乎是固定的。

此外，如果要查找的命令已定义为别名，则此操作将失败。

我的Debian服务器设置：

当多个包包含相同的名称时，我遇到了问题。

例如apache2。这就是我的解决方案：

function _apt_install() {
    apt-get install -y $1 > /dev/null
}

function _apt_install_norecommends() {
    apt-get install -y --no-install-recommends $1 > /dev/null
}
function _apt_available() {
    if [ `apt-cache search $1 | grep -o "$1" | uniq | wc -l` = "1" ]; then
        echo "Package is available : $1"
        PACKAGE_INSTALL="1"
    else
        echo "Package $1 is NOT available for install"
        echo  "We can not continue without this package..."
        echo  "Exitting now.."
        exit 0
    fi
}
function _package_install {
    _apt_available $1
    if [ "${PACKAGE_INSTALL}" = "1" ]; then
        if [ "$(dpkg-query -l $1 | tail -n1 | cut -c1-2)" = "ii" ]; then
             echo  "package is already_installed: $1"
        else
            echo  "installing package : $1, please wait.."
            _apt_install $1
            sleep 0.5
        fi
    fi
}

function _package_install_no_recommends {
    _apt_available $1
    if [ "${PACKAGE_INSTALL}" = "1" ]; then
        if [ "$(dpkg-query -l $1 | tail -n1 | cut -c1-2)" = "ii" ]; then
             echo  "package is already_installed: $1"
        else
            echo  "installing package : $1, please wait.."
            _apt_install_norecommends $1
            sleep 0.5
        fi
    fi
}

which命令可能有用。男子谁

如果找到可执行文件，则返回0；如果找不到或不可执行，则返回1：

NAME

       which - locate a command

SYNOPSIS

       which [-a] filename ...

DESCRIPTION

       which returns the pathnames of the files which would
       be executed in the current environment, had its
       arguments been given as commands in a strictly
       POSIX-conformant shell. It does this by searching
       the PATH for executable files matching the names
       of the arguments.

OPTIONS

       -a     print all matching pathnames of each argument

EXIT STATUS

       0      if all specified commands are 
              found and executable

       1      if one or more specified commands is nonexistent
              or not executable

       2      if an invalid option is specified

这样做的好处是，它可以确定可执行文件在运行环境中是否可用-这节省了一些问题。。。