#!/bin/sh echo "Hex $1 is decimal $((16#$1))"
#!/bin/sh echo "Hex $1 is decimal $(echo "ibase=16; $1" | bc)"
Your script uses a shell feature not supported by the shebang. Either rewrite the script to be portable, or change the shebang to explicitly require a shell like Bash.
In this case, using radix specifiers in arithmetic contexts, such as
$((16#DEADBEEF)) is not portable.
bc ibase/obase can be used instead.
ShellCheck is a static analysis tool for shell scripts. This page is part of its documentation.