why would "tr --complement --squeeze-repeats ..." append the substitution char once more? ...

[Albretch Mueller <lbrtchx@gmail.com>]

echo "abc123" > file.txt
ftype=$(file --brief file.txt)
echo "// __ \$ftype: |${ftype}|"
ftypelen=${#ftype}
echo "// __ \$ftypelen: |${ftypelen}|"

# removing spaces ...
ftype2=$(echo "${ftype}" | tr --complement --squeeze-repeats
'[A-Za-z0-9.]' '_');
echo "// __ \$ftype2: |${ftype2}|"
ftype2len=${#ftype2}
echo "// __ \$ftype2len: |${ftype2len}|"

lbrtchx