Often a wildcard test on files is needed.
Because test -f ... or [ -f ... ] have problems with zero or many arguments, and even [[ -f ... ]] has problems, and I have seen some ugly work-arounds,
I suggest the following simple function, to be defined somewhere at the beginning of the script:

Code:

file_exists() {
  for _i do [ -f "$_i" ] && return
  done
  return 1
}

It returns status 0 (success) if at least one of the given files was found,
and status 1 otherwise (the return 1 is necessary in case the nullglob option is on).
Examples:

Code:

if file_exists /tmp/*
then
  echo "at least one file is in /tmp"
fi

Code:

if file_exists /usr/lib/libtcl.so* /usr/lib/libtcl[0-9]*.so*
then
  echo "a libtcl is in /usr/lib"
fi

Analogue to file_exists() one can have the functions

Code:

dir_exists() {
  for _i do [ -d "$_i" ] && return
  done
  return 1
}

and

Code:

file_executable () {
  for _i do [ -f "$_i" -a -x "$_i" ] && return
  done
  return 1
}