☰

用于任意“PATH”类变量的“pathmunge”函数

tag-icon • tag-icon bash
用于任意“PATH”类变量的“pathmunge”函数

我确信你们中的许多人都熟悉pathmungeBourne shell 兼容的点文件中使用的规范函数，以防止变量中出现重复条目PATH​​。我还为LD_LIBRARY_PATH和变量创建了类似的函数MANPATH，因此我的 中有以下三个函数.bashrc：

# function to avoid adding duplicate entries to the PATH
pathmunge () {
    case ":${PATH}:" in
        *:"$1":*)
            ;;
        *)
            if [ "$2" = "after" ] ; then
                PATH=$PATH:$1
            else
                PATH=$1:$PATH
            fi
    esac
}

# function to avoid adding duplicate entries to the LD_LIBRARY_PATH
ldpathmunge () {
    case ":${LD_LIBRARY_PATH}:" in
        *:"$1":*)
            ;;
        *)
            if [ "$2" = "after" ] ; then
                LD_LIBRARY_PATH=$LD_LIBRARY_PATH:$1
            else
                LD_LIBRARY_PATH=$1:$LD_LIBRARY_PATH
            fi
    esac
}

# function to avoid adding duplicate entries to the MANPATH
manpathmunge () {
    case ":${MANPATH}:" in
        *:"$1":*)
            ;;
        *)
            if [ "$2" = "after" ] ; then
                MANPATH=$MANPATH:$1
            else
                MANPATH=$1:$MANPATH
            fi
    esac
}

有没有什么优雅的方法可以将这三个功能合二为一，以保持文件.bashrc更小？也许我可以通过一种方式传递要检查/设置的变量，类似于 C 中的引用传递？

答案1

您可以使用eval已知变量名称来获取和设置变量的值；以下函数在 Bash 和短跑：

varmunge ()
{
  : '
  Invocation: varmunge <varname> <dirpath> [after]
  Function:   Adds <dirpath> to the list of directories in <varname>. If  <dirpath> is
              already present in <varname> then <varname> is left unchanged. If the third
               argument is "after" then <dirpath> is added to the end of <varname>, otherwise
               it is added at the beginning.
  Returns:    0 if everthing was all right, 1 if something went wrong.
  ' :
  local pathlist
  eval "pathlist=\"\$$1\"" 2>/dev/null || return 1
  case ":$pathlist:" in
    *:"$2":*)
      ;;
    "::")
      eval "$1=\"$2\"" 2>/dev/null || return 1
      ;;
    *)
      if [ "$3" = "after" ]; then
        eval "$1=\"$pathlist:$2\"" 2>/dev/null || return 1
      else
        eval "$1=\"$2:$pathlist\"" 2>/dev/null || return 1
      fi
      ;;
  esac
  return 0
}

答案2

在 Bash 4.3 或更高版本中，您可以使用 来declare -n通过引用有效地传递变量。

# function to avoid adding duplicate entries to the PATH
pathmunge () {
    declare -n thepath=$1
    case ":${thepath}:" in
        *:"$2":*)
            ;;
        *)
            if [ "$3" = "after" ] ; then
                thepath=$thepath:$2
            else
                thepath=$2:$thepath
            fi
            ;;
    esac
}

你可以这样称呼它：

pathmunge PATH ~/bin

pathmunge MANPATH /usr/local/man after

相关内容