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Ascii value of character?

 
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# 1  
Old 09-09-2008
Ascii value of character?
Is there a way to determine the ascii value of a character? For example, let's say a shell variable has the value 'A'. I would like it's ascii value (e.g. 65 in this case). I would like to do this from a script (preferably ksh).
# 2  
Old 09-09-2008
I just stumbled upon the following...

$ printf "%d" "'A"

This will give me 65, so likewise I can certainly do this...

$ var=A
$ printf "%d" "'${var}"

What I don't understand is the single quote immediately preceding the character. This is the only way it'll work, but I've never seen that syntax before. I quickly glanced at the man pages for printf and I still don't fully understand this. Can someone please explain? Thank you.
# 3  
Old 09-09-2008
Single quotes like 'A' around a character is the convention used in the C language to distinguish a character from a string of characters like "A" which is enclosed in double quotes. That's all there is to it.
# 4  
Old 09-09-2008
Quote:
Originally Posted by shamrock
Single quotes like 'A' around a character is the convention used in the C language to distinguish a character from a string of characters like "A" which is enclosed in double quotes. That's all there is to it.
This is not a "pair" of single quotes. It's simply a single quote (by itself) preceding the character (i.e. 'A) . That's what I've never seen before. In fact, if you use a pair of single quotes, the conversion to the ascii value does not work.
# 5  
Old 09-10-2008
Interesting. From info printf...
Quote:
* If the leading character of a numeric argument is `"' or `'' then
its value is the numeric value of the immediately following
character. Any remaining characters are silently ignored if the
`POSIXLY_CORRECT' environment variable is set; otherwise, a
warning is printed. For example, `printf "%d" "'a"' outputs `97'
on hosts that use the ASCII character set, since `a' has the
numeric value 97 in ASCII.
# 6  
Old 09-10-2008
This is slightly off topic, but may give a clue:


I use a report generation program (CyberQuery). One option is to output the report as an Excel document.

Within Excel, if any cell of the document is all digits, but the source field was Aplha format, the data is preceeded by a single quote.

On the spreadsheet you see the data, including leading zeros (if any), but you do not see the leading quote.

Only when you select one of those cells, and look up to the cell contents field, do you see the single leading quote.


Hope that helps, or at least gives you something to research / consider.
# 7  
Old 09-10-2008
From POSIX.1-2001 ..
Quote:
The argument operands will be treated as strings if the corresponding conversion character is b, c or s; otherwise, it will be evaluated as a C constant, as described by the ISO C standard, with the following extensions:

* If the leading character is a single- or double-quote, the value will be the numeric value in the underlying codeset of the character following the single- or double-quote.
 
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