grep command trying to fetch numeric value

Question

From below text in file:

current_build: 22
previous_build: 55

I am only trying to grep number value of current_build.

When run following command

grep -o -E '[0-9]+' textfile

The output is both number like below

22    
55

How do i only grep the value 22

Answer 1

With GNU grep:

grep -Po 'current_build: \K.*' file

\\K : removes matching part before \\K

Output:

22

Answer 2

I would use awk because it is portable in opposite to grep -o which only works with GNU grep:

awk '/current_build/{print $NF}' file

awk splits the input into fields . The default field separator is a sequence of blank chars. NF is the number of fields , $NF is the last field.

Answer 3

仅在行首打印与current_build匹配的行，并在最后一个空格之后显示部分：

sed -n 's/current_build:.* //p' file