OS X (Apple)

 num=${TEST_VAL#??}
 lz=${num%%[1-9]*}
 TEST_VAL=${num#$lz}

#!/usr/local/bin/dash
# lead_zeros.sh

# This is a gotcha...
# There will always be 6 zeros sooner or later, 000000.
 
# Only the last 6 digits are really needed... 
TEST_VAL=0.000000
TEST_NUM=123

num=${TEST_VAL#??}
echo "${num}"
lz=${num%%[1-9]*}
echo "${lz}"
TEST_VAL=${num#$lz}

echo "Test value = ${TEST_VAL}..."

TEST_VAL=$(( TEST_VAL * TEST_NUM ))

echo "Required integer = ${TEST_VAL}..."

Last login: Mon Jan 20 21:18:42 on ttys000
AMIGA:amiga~> cd Desktop/Code/Shell
AMIGA:amiga~/Desktop/Code/Shell> chmod 755 lead_zeros.sh
AMIGA:amiga~/Desktop/Code/Shell> ./lead_zeros.sh
000000
000000
Test value = ...
./lead_zeros.sh: 19: ./lead_zeros.sh: Illegal number: 
AMIGA:amiga~/Desktop/Code/Shell> _