如何找到特定格式的数字并筛选出一定范围的值？

Question

如何找到格式0.xzy 0.xzy的数字，其中xzy是数字，x是8-9并在每次匹配（包括）之前将5行写到outputfile.txt 。

Answer 1

Find numbers in format 0.xzy ( xzy are numbers)

grep "^0.[0-9][0-9][0-9]$" file

Find cases where x is 8-9

grep "^0.[89][0-9][0-9]$" file

Answer 2

To find numbers in the format 0.xzy (using word boundaries not forcing whole line match) and print the 5 line preceding the match -B5 and redirect the output to outfile :

$ grep -B5 -Ew '0\.[0-9]{3}' file > outfile

# fix x to 8 or 9
$ grep -B5 -Ew '0\.[8-9][0-9]{2}' file > outfile

Note: the . needs escaping to mean a literal period otherwise 01234 will match. You will find man grep very helpful!