Bash script with regex and capturing group-CodePudding

I'm working on a bash script to rename automatically files on my Synology NAS.

I have a loop for the statement of the files and everything is ok until I want to make my script more efficient with regex.

I have several bits of code which are working like as expected:

filename="${filename//[-_.,\']/ }"
filename="${filename//[éèēěëê]/e}"

But I have this:

filename="${filename//t0/0}"
filename="${filename//t1/1}"
filename="${filename//t2/2}"
filename="${filename//t3/3}"
filename="${filename//t4/4}"
filename="${filename//t5/5}"
filename="${filename//t6/6}"
filename="${filename//t7/7}"
filename="${filename//t8/8}"
filename="${filename//t9/9}"

And, I would like to use captured group to have something like this:

filename="${filename//t([0-9]{1,2})/\1}"
filename="${filename//t([0-9]{1,2})/${BASH_REMATCH[1]}}"

I've been looking for a working syntax without success...

CodePudding user response：

The shell's parameter expansion facility does not support regular expressions. But you can approximate it with something like

filename=$(sed 's/t\([0-9]\)/\1/g' <<<"$filename")

This will work regardless of whether the first digit is followed by additional digits or not, so dropping that requirement simplifies the code.

CodePudding user response：

If you want the last or all t[0-9]{1,2}s replaced:

$ filename='abt1cdt2eft3gh'; [[ "$filename" =~ (.*)t([0-9]{1,2}.*) ]] && filename="${BASH_REMATCH[1]}${BASH_REMATCH[2]}"; echo "$filename"
abt1cdt2ef3gh

$ filename='abt1cdt2eft3gh'; while [[ "$filename" =~ (.*)t([0-9]{1,2}.*) ]]; do filename="${BASH_REMATCH[1]}${BASH_REMATCH[2]}"; done; echo "$filename"
ab1cd2ef3gh

Note that the "replace all" case above would keep iterating until all t[0-9]{1,2}s are changed, even ones that didn't exist in the original input but were being created by the loop, e.g.:

$ filename='abtt123de'; while [[ "$filename" =~ (.*)t([0-9]{1,2}.*) ]]; do filename="${BASH_REMATCH[1]}${BASH_REMATCH[2]}"; echo "$filename"; done
abt123de
ab123de

whereas the sed script in @tripleee's answer would not do that:

$ filename='abtt123de'; filename=$(sed 's/t\([0-9]\)/\1/g' <<<"$filename"); echo "$filename"
abt123de