linux command wc

$ cat test.sh
#!/bin/bash

echo "shell args option"
echo "script name : $0"
echo "first args : $1"
echo "first args : $2"
echo "first args : $3"

echo "------- \$# demonstration"
echo "args number: $#"

echo "------- \$\$ demonstration"
echo "shell pid: $$"

echo "------- \$* demonstration"
for i in "$*";do
echo $i
done

echo "------- \$@ demonstration"
for i in "$@";do
echo $i
done

echo "------- \$- demonstration"
echo $-

$ cat test.sh | wc -l
27

it can be use for  statistics  line numbers