SCRIPT-0b-make-usernames

#!/bin/bash

# ---------------------------------------------------------------------
# Make the   students-01   students-02  ...  students
#   files containing student usernames, from the course roster
#   (CSV) files which must have been previously downloaded.
#
# The user of this script must:
#   -- BEFORE running this script:
#         Download course roster (CSV) files.
#   -- AFTER  running this script:
#         Add usernames as desired to the other username files:
#              instructors  assistants  others  temp
#
# Author:  David Mutchler.
# ---------------------------------------------------------------------

# ----------------------------------------------------------------------
# Get the values of the variables:
#      course             e.g.  csse120
#      term               e.g.  202030
#      data_folder        e.g.    DATA/DATA-csse120-202030
#      data_subfolders    e.g.  ( DATA   DATA-csse120-202030 )
#      repos_folder       e.g.    REPOS/REPOS-csse120-202030
#      repos_subfolders   e.g.  ( REPOS   REPOS-csse120-202030 )
#
# from the relevant files.
# ----------------------------------------------------------------------

if [ ! "${SET_CONSTANTS_HAS_RUN}" == "1" ]; then
   source SET_CONSTANTS
fi

# ---------------------------------------------------------------------
# Confirm that the DATA folder exists.  Exit with a warning if not.
# ---------------------------------------------------------------------

if [ ! -d "${data_folder}" ]; then
    echo ""
    echo "ERROR: The course and term are:"
    echo "   Course: ${course}"
    echo "   Term:   ${term}"
    echo "but there is no corresponding  DATA  subfolder"
    echo "   Subfolder: ${data_folder}"
    echo "Figure out what is wrong and re-run this script."
    echo "Nothing done."
    echo ""
    exit 1
fi

cd ${data_folder}

# ---------------------------------------------------------------------
# Confirm that there is at least one course roster (CSV) file.
#   Exit with a warning if not.
# ---------------------------------------------------------------------

course_rosters=( $(/bin/ls | grep "\.csv$") )

if [ ${#course_rosters[@]} == 0 ]; then
    echo ""
    echo "ERROR: There are no course rosters (i.e., CSV files) in"
    echo "   ${data_folder}"
    echo "This script extracts usernames from such course rosters."
    echo "So if you are running this script, presumably there"
    echo "should be at least one such course roster."
    echo "Figure out what is wrong and re-run (or skip) this script."
    echo "Nothing done."
    echo ""
    exit 1
fi

# ---------------------------------------------------------------------
# For each course roster, make a corresponding   students-XX
# file with the usernames extracted from that course roster.
#   But do not overwrite an existing, non-empty file;
#   instead, show the result of a DIFF of the existing file
#   with the extracted usernames.
# ---------------------------------------------------------------------

for roster in ${course_rosters[@]}; do
    section=$(echo $roster | sed 's/.*-//')
    section=${section:0:2}

    students_file=students-${section}

    echo ""
    echo "Extracting usernames:"
    echo "   from course roster: ${roster}"
    echo "   into students file: ${students_file}"

    temp_file=temp-NOGOOD-THROW-THIS-AWAY-${roster}
    /bin/rm -f ${temp_file}

    # Extract the usernames into the temporary file:
    cat ${roster} | sed '1,4d' | sed 's/^"//' | sed 's/".*$//' > ${temp_file}

    # Careful! Do not overwrite an existing, non-empty students file!

    if [ ! -s students-${section} ]; then

        # The students file is new (or empty).
        # Put the extracted usernames into it.

        /bin/mv ${temp_file} ${students_file}
        number_of_students="`cat ${students_file} | wc -l`"
        echo "   OK! New file ${students_file} was created."
        echo "   It now contains ${number_of_students} usernames."

    elif [ "$( diff -q  ${students_file} ${temp_file} )" == "" ]; then
        
        # The students file exists but it has the same usernames
        # as those extracted from the course roster.
        # No action needed.

        number_of_students="`cat ${students_file} | wc -l`"
        echo "   OK! The students file already exists but it has"
        echo "   the same usernames as those extracted from the course roster."
        echo "   It still has ${number_of_students} usernames."

    else
        echo ""
        echo "   WARNING: the students file exists and is non-empty."
        echo "   I will NOT overwrite that file.  Here is a DIFF of"
        echo "   the existing file with the usernames in the course roster."

        diff ${students_file} ${temp_file}
        echo ""
        echo "   If you want to overwrite ${students_file}"
        echo "   with the usernames extracted from the course roster,"
        echo "   remove ${students_file} and then re-run this script."
    fi

    /bin/rm -f ${temp_file}
done


# ---------------------------------------------------------------------
# If there is not already a non-empty   students   file,
# make it, filling it with the concatenation of the students-XX files.
# ---------------------------------------------------------------------

echo ""
if [ ! -s students ]; then
    cat students-* > students
    number_of_students="`cat students | wc -l`"
    echo "I have created a   students   file that contains"
    echo "   the usernames in the combined students-XX files."
    echo "   It now contains ${number_of_students} usernames."
else
    number_of_students="`cat students | wc -l`"

    echo "There is an existing, non-empty   students"
    echo "   file that contains ${number_of_students} usernames."
    echo "   I will NOT overwrite it. If you want it to"
    echo "   incorporate changes that this script made,"
    echo "   delete the existing   students   file"
    echo "   and re-run this script."
fi

echo ""
echo "*** REMINDER: ***"
echo "Edit the files:"
echo ""
ls | grep -v '\.csv$'
echo ""
echo "as desired.  Add more files as desired."
echo ""
echo "For all subsequent scripts, you will specify"
echo "which of those username files you wish to use."
echo ""

# ---------------------------------------------------------------------
# Undo the CD done previously in this script.
# ---------------------------------------------------------------------

for folder in ${data_subfolders[@]}; do
    cd ..
done