Bash last index of
The bash
man page section titled "Variable Substitution" describes using ${var#pattern}
, ${var##pattern}
, ${var%pattern}
, and ${var%%pattern}
.
Assuming that you have a variable called filename
, e.g.,
filename="artifact-1.2.3.zip"
then, the following are pattern-based extractions:
% echo "${filename%-*}"artifact% echo "${filename##*-}"1.2.3.zip
Why did I use ##
instead of #
?
If the filename could possibly contain dashes within, such as:
filename="multiple-part-name-1.2.3.zip"
then compare the two following substitutions:
% echo "${filename#*-}"part-name-1.2.3.zip% echo "${filename##*-}"1.2.3.zip
Once having extracted the version and extension, to isolate the version, use:
% verext="${filename##*-}"% ver="${verext%.*}"% ext="${verext##*.}"% echo $ver1.2.3% echo $extzip
$ a="artifact-1.2.3.zip"; a="${a#*-}"; echo "${a%.*}"
‘#
pattern’ removes pattern so long as it matches the beginning of $a
.The syntax of pattern is similar to that used in filename matching.In our case,
*
is any sequence of characters.-
means a literal dash.- Thus
#*-
matches everything up to, and including, the first dash. - Thus
${a#*-}
expands to whatever$a
would expand to,except thatartifact-
is removed from the expansion,leaving us with1.2.3.zip
.
Similarly, ‘%
pattern’ removes pattern so long as it matches the end of the expansion.In our case,
.
a literal dot.*
any sequence of characters.- Thus
%.*
is everything including the last dot up to the end of the string. - Thus if
$a
expands to1.2.3.zip
,then${a%.*}
expands to1.2.3
.
Job done.
The man page content for this is as follows (at least on my machine, YMMV):
${parameter#word} ${parameter##word} The word is expanded to produce a pattern just as in pathname expansion. If the pattern matches the beginning of the value of parameter, then the result of the expansion is the expanded value of parameter with the shortest matching pattern (the ``#'' case) or the longest matching pattern (the ``##'' case) deleted. If parameter is @ or *, the pattern removal operation is applied to each positional parameter in turn, and the expansion is the resultant list. If parameter is an array variable subscripted with @ or *, the pattern removal operation is applied to each member of the array in turn, and the expansion is the resultant list. ${parameter%word} ${parameter%%word} The word is expanded to produce a pattern just as in pathname expansion. If the pattern matches a trailing portion of the expanded value of parameter, then the result of the expansion is the expanded value of parameter with the shortest matching pat- tern (the ``%'' case) or the longest matching pattern (the ``%%'' case) deleted. If parameter is @ or *, the pattern removal operation is applied to each positional parameter in turn, and the expansion is the resultant list. If parameter is an array variable subscripted with @ or *, the pattern removal operation is applied to each member of the array in turn, and the expansion is the resultant list.
HTH!
EDIT
Kudos to @x4d for the detailed answer.Still think people should RTFM though.If they don't understand the manual,then post another question.
Using Bash RegEx feature:
>str="artifact-1.2.3.zip"[[ "$str" =~ -(.*)\.[^.]*$ ]] && echo ${BASH_REMATCH[1]}