I do not understand how/why the following code is used. Please do not simply refer me to the man pages since I have already reviewed them extensively. Thank you.

exit 2 , exit 3, exit 0

I understand the basics of why the exit command is used, but I still don't understand what the significance/meaning of exit 2, exit 3, and exit 0 are.

The creation (and later deletion) of a temporary file

I understand that creation of the temporary file is used to print the contents of the following commands within that file so the grep command can be used to calculate our echoed results that we want, BUT, isn't there a better way to do it so we don't have to create/delete a file?

ls -log "$1" | awk '{print $1}' | grep -v total > $TF

I understand how the first part is piped to the awk, but I do not understand how the awk command is printing only the first column of information.
As far as the "grep -v total" goes, am I correct in that that command basically says to print to screen only those lines within that first column that do NOT contain the word "total"?

f_count=$(grep -c "-........." $TF

I do not understand why this will not work, however, it also doesn't seem like the best way to accomplish counting the number of files within the specified directory.

#!/bin/sh

# Check correct number of arguments (one)
# "$#" Stores the # of command-line arguments passed to shell program
if [ $# -ne 1 ]
then
  echo "Usage: homework4.sh <directory_name>"
  exit 2
# Check for directory existence
else
  if [ ! -d "$1" ]
  then
    echo "$1: No such directory"
    exit 3
  fi
fi

# Set up a temporary file name
TF=/tmp/$0.tmp

# Prints only the permissions of all files and directories to $TF
ls -log "$1" | awk '{print $1}' | grep -v total > $TF
# Count (-c) the number of lines where the character ("d", "r", etc.) exists
d_count=$(grep -c "d" $TF)
f_count=$(grep -c "-........." $TF)
r_count=$(grep -c "r" $TF)
w_count=$(grep -c "w" $TF)
x_count=$(grep -c "x" $TF)
# Print the results to screen
echo -n "In the directory "; pwd
echo "  Number of directories     : $d_count"
echo "  Number of files           : $f_count"
echo "  Number of readable items  : $r_count"
echo "  Number of writable items  : $w_count"
echo "  Number of executable items: $x_count"

# Remove temporary file
rm $TF
exit

The above code has been modified extensively by me and shows the final attempts of my efforts.

The Florida State University, Tallahassee Florida, USA, William Street, COP3353 (ww2.cs.fsu.edu/~street/cop3353/hw/hw04.html)