How to check if string contain alphabetic characters or alphabetic characters and numbers?

Question

I want to test STR contain alphabetic as (a-z) (A-Z) or alphabetic with numbers

meanwhile I have this

[[ "$STR"  =~ [a-zA-Z0-9] ]] && echo "contain alphanumerics"

but this works even STR have only numbers

while we want to print only if STR is contain alphabetic or alphabetic & numbers"

example

will print on the following case

gstfg523
HGFER34
JNF
GFGTVT
83bfF

will not print on

2424
4356
632
@65$
&%^$
82472243(*

Solution 1

Judging from the examples, I think you want to check that $STR is

• fully alphanumeric (nothing but letters and numbers), and
• not completely made of numbers (there is least one letter)?

Implementing those conditions:

[[ "$STR" =~ ^[[:alnum:]]*$ ]] && [[ ! "$STR" =~ ^[[:digit:]]+$ ]] && echo ok

This will also accept the empty string. To change that, use + instead of * in the first pattern.

Tests:

$ for STR in "" . .x .9 x x9 9 ; do 
    echo -en "$STR\t"; 
    [[ "$STR" =~ ^[[:alnum:]]*$ ]] && [[ ! "$STR" =~ ^[[:digit:]]+$ ]] && echo ok || echo not ok ; 
  done 
        ok
.       not ok
.x      not ok
.9      not ok
x       ok
x9      ok
9       not ok

Solution 2

For alnums with at least one alpha, that would be:

[[ $STR =~ ^[[:alnum:]]*[[:alpha:]][[:alnum:]]*$ ]]

(note that contrary to @ilkkachu's answer, that also excludes the empty string).

Or POSIXly:

valid() case $1 in
  (*[![:alnum:]]*) false;;
  (*[[:alpha:]]*) true;;
  (*) false;;
esac

valid "$STR" || printf >&2 '"%s" is not valid\n' "$STR"

Solution 3

If it is alphanumeric and not only numbers:

[[ "$STR"  =~ ^[a-zA-Z0-9]+$ ]] && [[ ! "$STR"  =~ ^[0-9]+$ ]] && echo …

Comments

[ivanivan]

alphanumeric is letters and numbers. If your string has to check both, check for letters and then check for numbers (or reverse order).

[jango]

ok my target is to check alphanomeic but it will not print if str is only numbers

[ilkkachu]

So, $STR must be fully alphanumeric (nothing but letters and numbers), and not completely made of numbers (at least one letter)?

[RomanPerekhrest]

@jango, is your string always comprised of multiline text?

[jango]

why it print also in case - STR=Jkk@@

[jango]

can you update the answer - if we want only alphabet or alphabet with numbers?

[done]

@jango Answer updated.