filename="example.txt"
filename_without_extension="${filename%.*}"
echo "$filename_without_extension"

Ejemplo de uso para formar urls de imagenes de Archive:

for i in $(ls *.jpg); do echo "<a href=\"https://archive.org/download/tag_name/$i\"><img src=\"https://archive.org/download/tag_name/${i%.*}_thumb.jpg\"></a>"; done