How can I check if a program exists from a Bash script?

Question

How would I validate that a program exists, in a way that will either return an error and exit, or continue with the script?

It seems like it should be easy, but it\

Answer 1

Expanding on @lhunath's and @GregV's answers, here's the code for the people who want to easily put that check inside an if statement:

exists()
{
  command -v "$1" >/dev/null 2>&1
}

Here's how to use it:

if exists bash; then
  echo 'Bash exists!'
else
  echo 'Your system does not have Bash'
fi