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Full Discussion: how to test for backspace
Top Forums UNIX for Dummies Questions & Answers how to test for backspace Post 302398182 by karthigayan on Wednesday 24th of February 2010 02:23:30 AM
Old 02-24-2010
MySQL Use ASCII
There is no straight forward way to compare the backspace.But there are some other way like ,converting the character to ascii value and compare that with particular ascii value of the backspace.

ascii value of the backspace is 8.But when I print the ascii value of backspace in my system it prints 127.it is the ascii value of DEL.So I used 127 in my code.You just change that value to 8 if needed.

Code:
read -n 1 x
x=`echo $x | tr -d "\n" | od -An -t dC`
if [ $x  -eq 127 ]; then # Change the 127 to 8 if it need
echo "backspace detected"
else
echo "some other character"
fi

Thanks
 

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LEARN ABOUT MINIX

bsfilt

BSFILT(1)						      General Commands Manual							 BSFILT(1)

NAME

       bsfilt, colcrt - a colcrt-like backspace filter

SYNOPSIS

       bsfilt [ - ] [ -U ] [ file ... ]

DESCRIPTION

       Bsfilt  filters	backspace  sequences from the input file(s) (standard input if none) in an approximation of colcrt(1).	Both the backspace
       and the character it returns to are removed, unless they form an underline sequence.  Underline sequences are treated according to the set-
       tings of the - and -U options.

OPTIONS

       -      specifies  that no underlining of any kind is to be propagated.  Without this option or the -U option, bsfilt approximates underlin-
	      ing with minus signs (`-') in following lines.

       -U     specifies that underlining with underscore (`_') and backspace (`) character sequences is permitted.

SEE ALSO

       cawf(1), colcrt(1) and nroff(1).

DIAGNOSTICS

       Diagnostic messages are delivered to the standard error file.

HISTORY

       Vic Abell of Purdue University wrote bsfilt to have a backspace filter for cawf(1) that is independent of licensed source code.

BUGS

       The maximum length of a line that can be underlined with minus signs is fixed.

       Bsfilt does not examine the characters that are being overprinted via backspace operations.  Thus, overprinting that is intended to form  a
       new  character  from  several  different  ones  is ineffective and only the last character of the sequence is propagated - e. g., ``o^H+'',
       intended to look like a bullet, is reduced to `+'.

								  February, 1991							 BSFILT(1)
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