extract the value from the log using shell script

With GNU grep:

grep -Po '[^ ]*(?=\.$)' file

grep -Po 'user \K[^ ]*' file

With awk:

awk -F "[. ]" '{print $(NF-1)}' file

awk -F "user " '{split($2,array," "); print array[1]}' file

or search for field with string user and print next field:

awk '{for(i=1; i<=NF; i++) if ($i=="user") print $(i+1) }' file

Output:

a8197zz

bash shell awk sed grep

Try this sed command also

sed 's/.*user \([^ ]\+\).*/\1/' fileName

Output:

a8197zz

bash shell awk sed grep

Following awk may help you in same.

awk '{sub(/\./,"",$NF);print $NF}'  Input_file

Output will be as follows.

a8197zz

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