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Operating Systems Linux Ubuntu Bash to ash port, character-matching problem Post 302910278 by Scrutinizer on Wednesday 23rd of July 2014 11:52:28 AM
Old 07-23-2014
A case statement will work in any Bourne type shell. This also makes it easy to test for an empty variable..
Code:
printf "Username: "
read _username
case $_username in 
  (*[![:alnum:]]*|"") 
    echo "invalid" ;;
  (*) 
    echo "valid"
esac

Note that will also allow letters with accents like é and ã
To exclude those, you could use (*[!a-zA-Z0-9]*|"") but that may not work properly because of a locale collation order...

--
Also note hat the proper negation character with character sets used in patterns is ! not ^ (even though it probably will work too)

Last edited by Scrutinizer; 07-23-2014 at 02:34 PM..
 

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COLORS(3)						   libbash colors Library Manual						 COLORS(3)

NAME
colors -- libbash library for setting tty colors. SYNOPSIS
colorSet <color> colorReset colorPrint [<indent>] <color> <text> colorPrintN [<indent>] <color> <text> DESCRIPTION
General colors is a collection of functions that make it very easy to put colored text on tty. The function list: colorSet Sets the color of the prints to the tty to COLOR colorReset Resets current tty color back to normal colorPrint Prints TEXT in the color COLOR indented by INDENT (without adding a newline) colorPrintN The same as colorPrint, but trailing newline is added Detailed interface description follows. Available colors: Green Red Yellow White The color parameter is non-case-sensitive (i.e. RED, red, ReD, and all the other forms are valid and are the same as Red). FUNCTIONS DESCRIPTIONS
colorSet <color> Sets the current printing color to color. colorReset Resets current tty color back to normal. colorPrint [<indent>] <color> Prints text using the color color indented by indent (without adding a newline). Parameters: <indent> The column to move to before start printing. This parameter is optional. If ommitted - start output from current cursor position. <color> The color to use. <color> The text to print. colorPrintN [<indent>] <color> The same as colorPrint, except a trailing newline is added. EXAMPLES
Printing a green 'Hello World' with a newline: Using colorSet: $ colorSet green $ echo 'Hello World' $ colorReset Using colorPrint: $ colorPrint 'Hello World'; echo Using colorPrintN: $ colorPrintN 'Hello World' AUTHORS
Hai Zaar <haizaar@haizaar.com> Gil Ran <gil@ran4.net> SEE ALSO
ldbash(1), libbash(1) Linux Epoch Linux
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