Search notes:

Bash: if

if evaluates a commands (CMD) exit status ($?). An exit status of 0 is considered true, all other status are considered false.

if CMD; then
   ...
   ...
fi

if CMD; then
   ...
   ...
else
   ...
   ...
fi

if CMD; then
   ...
   ...
elif CMD2; then
   ...
   ...
else
   ...
   ...
fi

See also