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up vote 11 down vote favorite
3

How do I get the ASCII value of the alphabet?

For example, 97 for a?

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5 Answers

up vote 26 down vote accepted

Define these two functions (usually available in other languages):

chr() {
  [ "$1" -lt 256 ] || return 1
  printf "\\$(printf '%03o' "$1")"
}

ord() {
  LC_CTYPE=C printf '%d' "'$1"
}

Usage:

chr 65
A

ord A
65
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That's perfect!! –  xmpirate Sep 26 '13 at 8:35
    
@dmsk80: +1. For others like me who think they spot a typo: "'A" is correct whereas if you use "A" it will say : A: invalid number . It seems it's done on printf side (ie, in the shell, "'A" is indeed 2 chars, a ' and a A. Those are passed to printf. And in the printf context, it is converted to the ascii value of A, (and is finally printed as a decimal thanks to the '%d'. Use 'Ox%x' to show it in hexa or '0%o' to have it in octal)) –  Olivier Dulac Sep 26 '13 at 11:05
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up vote 8 down vote

You can see the entire set with:

$ man ascii

You'll get tables in octal, hex, and decimal.

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There's also an ascii package for debian-based distros, but (at least now) the question is tagged as bash, so these wouldn't help the OP. In fact, it's installed on my system and all I get from man ascii is its man page. –  Joe Sep 27 '13 at 21:47
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up vote 4 down vote

If you want to extend it to UTF-8 characters:

$ perl -CA -le 'print ord shift' 😈
128520

$ perl -CS -le 'print chr shift' 128520
😈

With bash, ksh or zsh builtins:

$ printf "\U$(printf %08x 128520)\n"
😈
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Did you intend to put a square box character or else then the original char is not being displayed in the post and is being replaced by a square box character. –  mtk Oct 2 '13 at 7:11
    
@mtk, You need a browser that displays UTF-8 and a font that has that 128520 character. –  Stephane Chazelas Oct 2 '13 at 7:13
    
I am on Latest Chrome, and don't think that it doesn't support UTF-8. Would like to know what browser you are on? –  mtk Oct 2 '13 at 8:53
    
@mtk, iceweasel on Debian sid. The font as confirmed by iceweasel's web console is "DejaVu Sans" and I've got ttf-dejavu ttf-dejavu-core ttf-dejavu-extra packages installed which come from Debian with upstream at dejavu-fonts.org –  Stephane Chazelas Oct 2 '13 at 9:10
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up vote 4 down vote

This works well,

echo "A" | tr -d "\n" | od -An -t uC
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Can you maybe add a small explanation? –  Bernhard Sep 26 '13 at 12:04
    
tr to remove "\n" (new line ) from the input. od is used to -t dC is to print in decimal character. –  Saravanan Sep 26 '13 at 12:42
    
echo -n suppresses trailing newline eliminating the need for tr -d "\n" –  Gowtham Sep 26 '13 at 16:59
    
@Gowtham, only with some implementations of echo, not in Unix compliant echos for instance. printf %s A would be the portable one. –  Stephane Chazelas Sep 27 '13 at 8:44
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up vote 1 down vote

I'm going for the simple (and elegant?) Bash solution:

for i in {a..z}; do echo $(printf "%s %d" "$i" "'$i"); done

For in a script you can use the following:

CharValue="A"
AscValue=`printf "%d" "'$CharValue"

Notice the single quote before the CharValue. It is obligated...

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1  
How is your answer different from dsmsk80's answer? –  Bernhard Sep 26 '13 at 14:35
    
My interpretation of the question is "how to get the ASCII values for the values of the alphabet". Not how to define a function to retrieve the ASCII value for one character. So my first answer is a short one-line command to get the ASCII values for the alphabet. –  phulstaert Sep 27 '13 at 7:26
    
I get your point, but I still think the bottom line of both answer is printf "%d". –  Bernhard Sep 27 '13 at 9:11
    
I agree this is a crucial part of the process to get to the result, yet i didn't wanted to make the assumption that xmpirate knew about the "for i in" and the use of a range. If he wanted a list, this could be a real time-saver ;-). Also, future readers might find my additions helpful. –  phulstaert Sep 27 '13 at 9:44
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