2 examples for inkscape
# Convert SVG to PDF without starting GUI
# (echo a.svg --export-pdf=a.pdf;
# echo b.svg --export-pdf=b.pdf) |
# DISPLAY= inkscape --shell
# your_comment_here
In order to get a cropped PDF use -D option.
# Convert an svg file to a png (or jpg) with this command:
inkscape -z -e file.png -w 64 -h 64 file.svg