cmd

python fmtr.py < foo.prototxt.template > foo.prototxt.template.prototxt name=bar; cat foo.prototxt.template.prototxt

fmtr.py

import sys
fmt_dict = { }
for arg in sys.argv[1:]:
    eq_pos = arg.find("=")
    if eq_pos == -1: raise ValueError( "missing = in arg:" + repr(arg) )
    fmt_dict[arg[:eq_pos]] = arg[eq_pos+1:]
sys.stdout.write( sys.stdin.read() % fmt_dict )

foo.prototxt.template

name: "%(name)s"