如何使用sed在shell中的一行中切换带有数字的单词

Question

I have a question regarding on how to switch a number (1-infinity) with a character or a word:

Here is my code:

sed  's/ ([a-z]*) ([0-9]*)/\2 \1/g'> $file_output

so I have the output (before using the command above) as

1 a
45 adam

and the intended output from using the sed command:

a 1
adam 45 

but the line wouldn't work, specifically due to a syntax error. Here is the error that comes up:

sed: -e expression #1, char 28: invalid reference \2 on `s' command's RHS

How can I achieve my desired output?

Answer 1

You need to backslash the parentheses to make them into grouping ones:

s/\([a-z]*\) \([0-9]*\)/\2 \1/g'

Or, if your sed supports it, use -r or -E to indicate you're using extended regular expressions.

Answer 2

使用sed 's/\\(.*\\) \\(.*\\)/\\2 \\1/'是将任何字母数字彼此转换的一般方法。