Grep variable for string in bash

Question

We'd like to search for clid=* (* stands for an number) in the following $test variable:

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error id=0 msg=ok

error id=0 msg=ok

cluid=something2384fjdfkj clid=1 name=me

error id=0 msg=ok

Final result should be clid=1 .

Answer 1

Use the following egrep command:

egrep -o '\bclid=[0-9]+\b' testfile

-o option, tells to print only matched substrings

\\b - word boundary

Answer 2

This will print clid followed by one or more number:

grep -oP 'clid=\d+' inputfile

Or if it the input is from variable then :

echo  $test  |grep -oP 'clid=\d+'

Answer 3

Bash 有所谓的here 字符串，它允许您将变量的内容提供给 grep，而无需echo或管道：

grep -Eo 'clid=[0-9]+' <<< "$test"