如何只保留一个空格的字符串并使用sed替换所有其他空格？

Question

• I have a data file (1.data) which contains the following:

    USSR 8649 BS275 Asia Cananda 3852 BS25 North America 

  What I want is to keep the string of only one space and replace all the other spaces with :

My sed code:

sed 's/ *   */:/g' 1.data

:USSR:8649:BS275:Asia
:Cananda:3852:BS25:North America

That works perfect.

Since I know A+ matches A, AA, AAA, AAAA and so on, I tried another regular expression.

sed 's/ *  +/:/g' 1.data



          USSR                  8649                 BS275                  Asia
       Cananda                  3852                  BS25         North America

However, it does not work. Nothing changes.

What mistake did I make?

Answer 1

添加选项-E （从正则表达式切换为扩展正则表达式）或将+替换为\\+ 。

Answer 2

sed would treat "+" as a normal character if no -r option is added. And "+" meta-character would match to one or more after -r: extended regular expressions is added. So your command can be modified as,

sed -r 's/[[:space:]]+/:/g' 1.data