Character to value works:
$ printf "%d\n" \'A 65 $ I have two questions, the first one is most important:
One line
printf "\x$(printf %x 65)" Two lines
set $(printf %x 65) printf "\x$1" Here is one if you do not mind using awk
awk 'BEGIN{printf "%c", 65}' 
printf "$(printf '\\x%02x' $char)"This works (with the value in octal):
$ printf '%b' '\101' A even for (some: don't go over 7) sequences:
$ printf '%b' '\'{101..107} ABCDEFG A general construct that allows (decimal) values in any range is:
$ printf '%b' $(printf '\\%03o' {65..122}) ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz Or you could use the hex values of the characters:
$ printf '%b' $(printf '\\x%x' {65..122}) ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz You also could get the character back with xxd (use hexadecimal values):
$ echo "41" | xxd -p -r A That is, one action is the reverse of the other:
$ printf "%x" "'A" | xxd -p -r A And also works with several hex values at once:
$ echo "41 42 43 44 45 46 47 48 49 4a" | xxd -p -r ABCDEFGHIJ or sequences (printf is used here to get hex values):
$ printf '%x' {65..90} | xxd -r -p ABCDEFGHIJKLMNOPQRSTUVWXYZ Or even use awk:
$ echo 65 | awk '{printf("%c",$1)}' A even for sequences:
$ seq 65 90 | awk '{printf("%c",$1)}' ABCDEFGHIJKLMNOPQRSTUVWXYZ 
seq 98 102 | awk 'BEGIN{print "\n\tDEC\tOCT\tHEX\tCharacter\n\t---\t---\t--\t-"}; {printf("\t%d\t%o\t%x\t%c\n",$1,$1,$1,$1)}; END{printf "\n"}' {Thanks also to this answer to a different question}For your second question, it seems the leading-quote syntax (\'A) is specific to printf:
If the leading character is a single-quote or double-quote, the value shall be the numeric value in the underlying codeset of the character following the single-quote or double-quote.
From https://pubs.opengroup.org/onlinepubs/9699919799/utilities/printf.html
One option is to directly input the character you're interested in using hex or octal notation:
printf "\x41\n" printf "\101\n" 
\r) in a bash script and I found I had to use the following: testchar=$'\r'; if [ ${testchar} = $'\r' ]; then echo "is true"; else echo "is false"; fi. ASCII hex can be used in place of \r, ie. $'\x0D'. However, the string "\r", or the hex equivalent, didn't work for the conditional, always returning false.
For this kind of conversion, I use perl:
perl -e 'printf "%c\n", 65;' 
If you want to save the ASCII value of the character: (I did this in BASH and it worked)
{ char="A" testing=$( printf "%d" "'${char}" ) echo $testing} output: 65
If you convert 65 to hexadecimal it's 0x41:
$ echo -e "\x41" A
$ printf "\x41"Here's yet another way to convert 65 into A (via octal):
help printf # in Bash man bash | less -Ip '^[[:blank:]]*printf' printf "%d\n" '"A' printf "%d\n" "'A" printf '%b\n' "$(printf '\%03o' 65)" To search in man bash for \' use (though futile in this case):
man bash | less -Ip "\\\'" # press <n> to go through the matches this prints all the "printable" characters of your basic bash setup:
printf '%b\n' $(printf '\\%03o' {30..127}) !"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~ 
\36 \37 and \177 are all that "printable" ?Here is a solution without eval nor $() nor `` :
ord () { local s printf -v s '\\%03o' $1 printf "$s" } ord 65 Given that there are not that many 1-byte characters, but only 256, they can quickly be precomputed at your script startup:
declare -ag CHARS=() for REPLY in {{0..9},{a..f}}{{0..9},{a..f}}; do printf -v CHARS[${#CHARS[@]}] "\x$REPLY" done (I reused the discardable REPLY variable, but you can local your own inside an init function)
Then...
$ echo "${CHARS[65]}" A $ i=65 $ echo "${CHARS[i]}" A Beware of \x00, whose value is not properly handled in Bash because it is the string terminator character:
$ var=$'qwe\x00rty' $ echo ${#var} 3 $ echo "<${var}>" <qwe> So, "${CHAR[0]}" will always be a problem under Bash.
This way, you avoid output capture, inline text substitution and re-parsing once and again for every time you need to process one character; which is even worse for subprocess IPC through xxd, awk or perl.
The following script prints aaa...zzz (i.e. aaa > aab > aac > ... > zzx > zzy > zzz)
for i in $(seq 0 25); do first=$(printf \\$(printf '%03o' $((97+i)) )) for f in $(seq 0 25); do second=$(printf \\$(printf '%03o' $((97+$f)) )) for g in $(seq 0 25); do third=$(printf \\$(printf '%03o' $((97+$g)) )) echo "${first}${second}${third}" done done done The core of the functionality here is that printf '%03o' 97 prints the octal value of 97 i.e. 141; and printf \\141 prints the character it corresponds to.
