I have a string like rev00000010 and I only want the last number, 10 in this case.

I have tried this:

echo "$TEST" | sed '/^[[:alpha:]][0]*/d'
echo "$TEST" | sed '/^rev[0]*/d'

both return nothing, although the regex seems to be correct (tried with regexr)


The commands you passed to sed mean: if a line matches the regex, delete it. That's not what you want.

echo "$TEST" | sed 's/rev0*//'

This means: on each line, remove rev followed by any number of zeroes.

Also, you don't need sed for such a simple thing. Just use bash and its parameter expansion:

shopt -s extglob         # Turn on extended globbing.
echo "${TEST##rev*(0)}"  # Remove everything from the beginning up to `rev`
                         # followed by the maximal number of zeroes.



Would remove every thing to the left of the left-most non-zero digit.


number=`expr "x$test" : 'xrev0*\(.*\)'`
  • The first will break with dots, hex, spaces, etc: test='rev 003A0.1056' will produce number="3A0.1056". The second will break on any space, the same value will produce: 003A0.1056 from the expr. – user79743 Aug 10 '15 at 6:03

If you already have the variable TEST just print it with all letter removed

printf "%.0f\n" ${TEST//[a-z]/}


printf "%g\n" ${TEST//[a-z]/}

Do not use %d or echo-command becouse numbers with leading 0 is understood as octal


A few more options (though I also recommend you use Parameter Expansion as suggested by @choroba):

  • Use sed or perl to replace everything but the last two characters with the last two characters. This effectively deletes everything except the last two.

    $ sed -r 's/.*(..)/\1/' <<<$TEST
    $ perl -pe 's/.*(..)/\1/' <<<$TEST
  • Set awk's field delimiter to 2 or more 0s and print the last field:

    $ awk -F"00+" '{print $NF}' <<<$TEST
  • Extract only the last two characters:

    $ grep -oP '..$' <<<$TEST
    $ perl -lne '/(..)$/; print $1' <<<$TEST
  • Print only the 10th-last bytes:

    $ cut -b 10- <<<$TEST

Note that all of the above use <<<$var which is a bash construct. To use it in other shells, change to echo "$TEST" | command.

  • 1
    For awk other variant which can avoid some problem awk -F"[a-z]" '{print +$NF}' – Costas Nov 13 '14 at 14:54

To get the "last number", select any sequence of digits at the end of the string, and convert it to a decimal number:

With Bash:

 [[ "$test" =~  ([1-9][0-9]*)$ ]] && echo "number: $((10#${BASH_REMATCH[1]}))"

With grep:

echo "$test" | grep -Po "[1-9][0-9]*$"

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