The following works lists all *.txt files in the current dir, except those that begin with a number.
This works in bash, dash, zsh and all other POSIX compatible shells.
for FILE in /some/dir/*.txt; do # for each *.txt file
case "${FILE##*/}" in # if file basename...
[0-9]*) continue ;; # starts with digit: skip
esac
## otherwise, do stuff with $FILE here
done
In line one the pattern /some/dir/*.txt will cause the for loop to iterate over all files in /some/dir whose name end with .txt.
In line two a case statement is used to weed out undesired files. – The ${FILE##*/} expression strips off any leading dir name component from the filename (here /some/dir/) so that patters can match against only the basename of the file. (If you're only weeding out filenames based on suffixes, you can shorten this to $FILE instead.)
In line three, all files matching the case pattern [0-9]*) line will be skipped (the continue statement jumps to the next iteration of the for loop). – If you want to you can do something more interesting here, e.g. like skipping all files which do not start with a letter (a–z) using [!a-z]*, or you could use multiple patterns to skip several kinds of filenames e.g. [0-9]*|*.bak to skip files both .bak files, and files which does not start with a number.