bash compare regex expression and not the variable - regex

Question

I want to remove all file contain a substring in a string, if does not contain, I want to ignore it, so I use regex expression
str=9009
patt=*v[0-9]{3,}*.txt
for i in "${patt}"; do echo "$i"
if ! [[ "$i" =~ $str ]]; then rm "$i" ; fi done
but I got an error :
*v[0-9]{3,}*.txt
rm: cannot remove '*v[0-9]{3,}*.txt': No such file or directory
file name like this : mari_v9009.txt femme_v9009.txt mari_v9010.txt femme_v9010.txt

Answer 1

bash filename expansion does not use regular expressions. See https://www.gnu.org/software/bash/manual/bash.html#Filename-Expansion
To find files with "v followed by 3 or more digits followed by .txt" you'll have to use bash's extended pattern matching.
A demonstration:
$ shopt -s extglob
$ touch mari_v9009.txt femme_v9009.txt mari_v9010.txt femme_v9010.txt
$ touch foo_v12.txt
$ for f in *v[0-9][0-9]+([0-9]).txt; do echo "$f"; done
femme_v9009.txt
femme_v9010.txt
mari_v9009.txt
mari_v9010.txt
What you have with this pattern for i in *v[0-9]{3,}*.txt is:
first, bash performs brace expansion which results in
for i in *v[0-9]3*.txt *v[0-9]*.txt
then, the first word *v[0-9]3*.txt results in no matches, and the default behaviour of bash is to leave the pattern as a plain string. rm tries to delete the file named literally "*v[0-9]3*.txt" and that gives you the "file not found error"
next, the second word *v[0-9]*.txt gets expanded, but the expansion will include files you don't want to delete.
I missed the not from the question.
try this: within [[ ... ]], the == and != operators are a pattern-matching operators, and extended globbing is enabled by default
keep_pattern='*v[0-9][0-9]+([0-9]).txt'
for file in *; do
if [[ $file != $keep_pattern ]]; then
echo rm "$file"
fi
done
But find would be preferable here, if it's OK to descend into subdirectories:
find . -regextype posix-extended '!' -regex '.*v[0-9]{3,}\.txt' -print
# ...............................^^^
If that returns the files you expect to delete, change -print to -delete

Answer 2

You need to remove the quotes in the for loop. Then the filename globs will be interpreted:
for i in ${patt}; do echo "$i"

Answer 3

I assume that you are using Python.
I have tested your regex code, and found the * character unnecessary.
The following seems to work fine: v[0-9]{3,}.txt
Can you please elaborate some more on the issue?
Thanks,
Bren.

Answer 4

I just piped the error message to /dev/null. This worked for me:
#!/bin/bash
str=9009
patt=*v[0-9]{3,}*.txt
rm $(eval ls $patt 2> /dev/null | grep $str)

Answer 5

This is not regex, this is globbing. Take a look what gets expanded:
# echo *v[0-9]{3,}*.txt
*v[0-9]3*.txt femme_v9009.txt femme_v9010.txt mari_v9009.txt mari_v9010.txt
*v[0-9]3*.txt obvously doesn't exists. can you clarify what files are you trying to achieve with {3,} ? Otherwise live it out and it will match the kind of filenames you have specified.
http://tldp.org/LDP/abs/html/globbingref.html