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TADASUKE
Asked: 2020-06-26 07:11:46 +0800 CST

“printf”格式：“空格”和“%-s\n”

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我正在学习 shell 脚本。在某些教程中有一个我无法理解的示例行。谁能告诉我下面代码中第一行的含义？

format="%8s%10s%10s   %-s\n"
printf "$format" "Dirs" "Files" "Blocks" "Directory"

total_dirs=$(find $HOME -type d | wc -l)
total_files=$(find $HOME -type f | wc -l)
total_blocks=$(du -s $HOME)

printf "$format" $total_dirs $total_files $total_blocks

我的问题是关于拳头线的下半场。

  1. 关于“空间”的使用：

如果 $3 和 $4 之间有 3 个空格，那么输出的行在 $3 和 $4 之间也有 3 个空格？

  1. 关于“%-s\n”部分：

此示例代码中的“-（连字符）”是什么意思？即使我删除了它，我也得到了相同的输出结果。

scripts command-line gnome-terminal bash gnome-shell

1 个回答

  1. Best Answer

    bash shell 内置从相应的C例程继承其格式说明符，因此最有用的参考通常是man 3 printf. 从那里：

    1. 是的，任何不属于格式说明符的字符都会按字面意思打印
       Format of the format string
       The format string is a character string, beginning and  ending  in  its
       initial  shift state, if any.  The format string is composed of zero or
       more  directives:  ordinary  characters  (not  %),  which  are   copied
       unchanged  to the output stream; and conversion specifications, each of
       which results in fetching zero or more subsequent arguments.  Each con‐
       version specification is introduced by the character %, and ends with a
       conversion specifier.  In between there may be (in this order) zero  or
       more  flags, an optional minimum field width, an optional precision and
       an optional length modifier.
    1. 它指定该值应左对齐
       -      The converted value is to be left adjusted on the  field  bound‐
          ary.  (The default is right justification.)  The converted value
          is padded on the right with blanks, rather than on the left with
          blanks or zeros.  A - overrides a 0 if both are given.
    • 1

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