Shell脚本在文件中查找和替换

Question

I have a file postmaster.log, in which I need to find pattern and change its value Pattern I need to find is

MaxValue=3 #this could be any value not just 3

I need to change its value to

MaxValue=0

Issue is there are also patterns like

"MaxValueSet=3" and "MaxValue is currently low" 

Which are also getting replaced.I only has to change MaxValue=3 to MaxValue=0 I tried using sed

 sed -i 's/MaxValue=3/MaxValue=0/g' /home/postmaster.log

But this only works if MaxValue=3 for anyother value it won't work.

Answer 1

use a regexp to catch MaxValue= followed by any number...

s/MaxValue=[0-9]+/MaxValue=0/g

should work.

Answer 2

It sounds like you want

sed -i 's/^MaxValue=.*/MaxValue=0/' /home/postmaster.log

which will find all lines that begin with MaxValue= , and replace each of those lines with MaxValue=0 .

Answer 3

您也可以限制sed的行数：

sed -i '/^MaxValue=/s/=[[:digit:]][[:digit:]]*/=0/' /home/postmaster.log