Make the regex find any word that contains at least one lower case letter

Question

How to fix this regex so it finds any word that contains at least one lower case letter grep -E -e '^[S][a-z]+, [^S][a-z]+' People.txt. The regex I am using know is to search for the second name that stars with capital S followed by comma and then space and then the first name that starts with any letter other than S. I want to fix this regex so it can also find a name like thisSbBBB, PaUU. I am using grep in the terminal of MacBook

Smith(second name) Paul(first name)

Text file

Smith, Paul
SbBBB, PaUU
Pau, Smi
Smi, Smi
SA, PA

The output of the regex

Smith, Paul
SbBBB, PaUU

Answer 1

This might be what you're trying to do, using any POSIX compliant grep and assuming you want to match English language upper case letters other than S for the start of the second word:

$ grep '^S[[:alpha:]]*[[:lower:]][[:alpha:]]*, [ABCDEFGHIJKLMNOPQRTUVWXYZ][[:alpha:]]*[[:lower:]][[:alpha:]]*' file
Smith, Paul
SbBBB, PaUU

Answer 2

$ grep -Px 'S\pL*\p{Ll}\pL*, (?!S)\p{Lu}\pL*\p{Ll}\pL*' < your-file
Smith, Paul
SbBBB, PaUU

Would report lines that start with S followed by any number of letters (characters with Letter property), followed by 1 lower case letter, followed by any number of letters followed by ", ", and an uppercase letter other than S and again a number of letters, at least one of which lower case.

PCRE \pL, like POSIX [[:alpha:]] is not limited to letters in alphabetic scripts; that includes word characters of any script. You could replace with [\p{Ll}\p{Lu}] to only match on letters that can be considered either lower or upper case or with \p{Latin} for any letter in the Latin script (as used in English, French, Spanish...) and (?=\p{Latin})\p{Ll} for a lower case letter in the Latin script only (not those in Greek, Cyrillic, etc scripts) for instance.

To use those [a-z] and only match on the 26 lowercase letters of the US ASCII charset, you'd need to fix the locale to C/POSIX and then you don't even need PCRE:

L='[A-Za-z]' Ll='[a-z]'
LC_ALL=C grep -x "S$L*$Ll$L*, [A-RT-Z]$L*$Ll$L*"

Note that it won't match on Serra, Éric for instance as that É is not matched by [A-RT-Z] in the C locale.