I want to strip all numeric characters from a String variable, eg from:
VARIABLE=qwe123rty567
to:
echo $VARIABLE
> qwerty
I've searched many posts but they either use sed to output to file/file names, or output to echo. I was not able to get it working with because of the white space:
VARIABLE=$VARIABLE | sed 's/[0-9]*//g'
With bash:
$ printf '%s\n' "${VARIABLE//[[:digit:]]/}"
qwerty
[:digit:] can contain other characters than 0 to 9 depend on your locale. If you want only to remove 0 to 9, use C locale instead.
[:digit:] might contain more or less than you would expect it to. If you only want the numbers 0 to 9, use LC_COLLATE=C and [0-9].
[:digit:] instead of [0-9].
[;digit:] == [0-9] though, so worth mentioning the pitfalls :-)
For variety, here's methods using
tr:
VARIABLE=$(printf '%s' "$VARIABLE" | tr -d '0123456789')
sed:
VARIABLE=$(printf '%s' "$VARIABLE" | sed 's/[0-9]//g')
Bash expansion, by far the most terse:
VARIABLE=${VARIABLE//[0-9]/}
and finally Bash expansion again, this time using the [[:digit:]] character class.
VARIABLE=${VARIABLE//[[:digit:]]/}
Note that (as others have pointed out) [[:digit:]], should cover anything defined as a digit in your locale.
//.../? Is it a normal regex? I tried //[0-9]{2}\$/ for two numbers at the end, to no success.
VARIABLE=qwe123rty567
IFS=0123456789
set -f # Disable glob
printf %s $VARIABLE
qwerty
further manipulation is possible.
VARIABLE=qwe123rty567
IFS=0123456789
set -f # Disable glob
set -- $VARIABLE
IFS=; VARIABLE=$*
printf "replaced $# numbers in \$VARIABLE. RESULT:\t%s\n" "$*"
replaced 6 numbers in $VARIABLE. RESULT: qwerty
echo which replaces nulls with spaces - like eval.
White space (actually, failure to quote your variables) was only part of the problem.
You can't just pipe a variable through sed like that, it doesn't work. More precisely, it doesn't pipe the value of "$VARIABLE" through sed, the shell will try to execute the value of "$VARIABLE" and pipe the output of that through sed. BTW, this is not a bug - this is useful if $VARIABLE happens to contain a valid command like ls or rsync or whatever.
Also, if you want to assign the ouput of a command or pipeline to a variable, you need to surround that command/pipeline with $().
So, to modify a variable with sed, you need to do something like this:
VARIABLE=$(printf '%s' "$VARIABLE" | sed 's/[0-9]*//g')
You could use echo there instead of printf but echo will interpret and act on certain character sequences in $VARIABLE (e.g. \t, \n, \r, etc), while printf won't. You'll run across a lot of examples using echo...replace them with printf '%s', it's much safer.
%s ?
%s by itself, no. more complicated format strings should be quoted, though, so it's a good habit to get into.
$VARIABLE, though.
VARIABLE=qwe123rty567? OK, right. I made my assessment ("failure to quote your variables") on the basis of none of the OP's examples having quotes around the variables, and the fact that he mentioned white-space as being a problem.