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allow only alphnumeric entry and an underscore

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# 1  
Old 06-09-2009
Question allow only alphnumeric entry and an underscore
I am taking an user input which should only be an alphanumeric character or an underscore. How to i do it?
# 2  
Old 06-09-2009
man regex.

you can use character class for that purpose.

Code:
[a-z0-9_]

or in general,
Code:
[_[:alnum:]]

# 3  
Old 06-09-2009
Code:
https://www.unix.com/shell-programming-scripting/44098-ksh-test-if-string-contains-alphanumeric.html

even this u can try :

Code:
echo 's$' | awk '$0 ~ /[^a-zA-Z0-9]/ { print "fail" }'

Last edited by panyam; 06-09-2009 at 10:21 AM..
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