[SOLVED] How to get the lines that include only a single group of letters using Bash?

Issue

I am trying to find the lines that include only one group of letters. The file includes only digits and lower case letters. No space or anything.

Good example:

39568250269955376311912572precondition005426787530581443236416842014020466976603

Bad example:

1895853531360579the3170095290529923mathematici2779805995331496368099837070an1084

Solution

Could you please try following.

awk 'gsub(/[a-z]+/,"&")==1' Input_file

Explanation: Adding explanation of above code, it is only for explaining purposes for running code kindly use above mentioned code itself.

awk '                    ##Starting awk program here.
gsub(/[a-z]+/,"&")==1    ##Using gsub function of awk to substitute all small letters occurrences with same values itself.
                         ##Then checking count of it,if it is equal to 1 then print current line.
                         ##awk works on method of condition and action, in above condition is mentioned but NO action so by default print of current line will happen.
' Input_file             ##mentioning Input_file name here, which is being passed to awk program.

Answered By - RavinderSingh13