I have a string structure like this bob-type-8.2-mp2-2017-93-43-11-65-48.spr form where I just need to extract 8.2-mp2-2017-93-43-11-65-48 .

It means the output string should contain all the characters after encountering the first numerical value and then removing the .spr from that.

How can I do that?

7 Answers 7


Try this:

echo "bob-type-8.2-mp2-2017-93-43-11-65-48.spr" | sed 's/^[^0-9]*//;s/\.[^.]*$//'

Output will:



Sed uses pattern 's/pattern/replace_pattern/' to find pattern and replace it to replace_pattern

So, pattern 's/^[^0-9]*//' get all symbols from start of line and before first digits occurance and replace it to nothing (replace_pattern are empty).

The next step - delete extention. We can do this with the same sed's pattern 's///'.

s/\.[^.]*$// - find all symbols that not a . at the end $ of line and replace it to nothing.

; - devide patterns.

For best understanding you could use this command instead:

echo "bob-type-8.2-mp2-2017-93-43-11-65-48.spr" | sed -e 's/^[^0-9]*//' -e 's/\.[^.]*$//'
  • Note that it assumes the file name doesn't contain newline characters (or bytes not forming valid characters, or backslash characters depending on the echo implementation) Oct 3, 2017 at 16:33

In Bash, with extglob:

$ shopt -s extglob
$ var=bob-type-8.2-mp2-2017-93-43-11-65-48.spr
$ res=${var##*([^0-9])}
$ res=${res%.spr}
$ echo "$res"

*([^0-9]) matches any string of non-digits, ${var##pattern} removes the longest matching pattern from the beginning of the string, ${var%pattern} removes the (shortest) matching pattern from the end.


another approach with sed.

sed 's/^[^[[:digit:]]*\(.*\)\.spr$/\1/' <<<"bob-type-8.2-mp2-2017-93-43-11-65-48.spr"
  • ^[^[[:digit:]]* match everything start from beginning of the string until first digit seen; Same as ^[^0-9]*

  • \(.*\) matches everything after above matches and parentheses \(...\) are used to capture a group match with \1 as its back-reference.

  • \.spr$ matches a literal point followed by spr at the end of input string.

  • \1 prints only captured group match.


So many sed answers! How about a pure bash solution using =~ pattern matching and the not-so-common back-reference array BASH_REMATCH?

# put your string in variable named 'input'
patt='^[^0-9]*(.*)\..*' && [[ $input =~ $patt ]] && echo "${BASH_REMATCH[1]}"

Just to stand apart from the crowd. ;)



  • ${string#pattern}: remove from the start of $string what is matched by pattern which in this case is:
  • ${string%%[0-9]*} $string stripped of its longest trailing part that matches the [0-9]* pattern. So that's the part up to the first digit.
  • ${newstring%.*}: $string stripped of its shortest trailing part that matches the .* pattern. So removes the extension.

With zsh:

  • ${string:r}: expands to the root name (removed the extension) like in csh
  • ${(M)var%%pattern}, return what is Matched by the %% operator (which without (M) would remove the longest part at the end that would match the pattern like in POSIX shells).

How about this?

echo bob-type-8.2-mp2-2017-93-43-11-65-48.spr | sed -r 's/^[^0-9]*(.*)\..*$/\1/'

This takes everything from the first numerical value encountered after the beginning of the string to the end of the string minus the last dot and what follows it.

  • ^[^0-9]* skips all non-numerical: NOT zero to nine ([^0-9]), 0 to N times (*), from the beginning of the line (^).
  • \..*$ matches any character (.), 0 to N times (*), before the end of the line ($), and preceeded by a dot (\.). In our case this is .spr but it could apply to any other "dot + N-characters" file extension: .s, .yaythatsacoolextension, etc, work as well.
  • (.*), referred as \1 later, keeps (this is the purpose of the parenthesis, we couldn't refer to it later otherwise) what's in the middle: any character (.), 0 to N times (*). This gives us 8.2-mp2-2017-93-43-11-65-48.

So if you need to list into a file the normalized names of all .spr contained in the current directory, for example, you can do something like this:

for i in *.spr
    echo $i | sed -r 's/^[^0-9]*(.*)\..*$/\1/' >> mylist.lst

And tomorrow, should you need to do that with .blop files instead, just turn the *.sprabove into *.blop.


Sed is one of the possible approaches

echo bob-type-8.2-mp2-2017-93-43-11-65-48.spr | sed 's/^[^0-9]*//;s/....$//'

regexps mean

  1. replace all non-numerical symbols from beginning with nothing till the first numerical
  2. replace last 4 chars with nothinig
  • yep, overseen that, updated now
    – Tagwint
    Oct 3, 2017 at 13:15

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