mess-allocation

#!/bin/bash

location='/home' # where the homedirs were created
messtxt="$location"/HAD/mess.txt



# `sed -i` creates a new file with the current user's
# UID/GID, which results in users not being able to
# edit their files as they are now owned by HAD.
# The workaround is to write to a temporary file, then
# `cat` that file into the original one.
tempfile=$(mktemp)

# If user is HAD, allocate messes to students
#
# Order of filing preferences is determined by
# the order of the rollnos appended to mess.txt
if [[ $(id -u) -eq $(id -u 'HAD') ]]; then

    messCapacities=() #index->messno.; value->capacity

    while IFS=' ' read -r num cap; do
        messCapacities[num]=$cap
    done < "$messtxt"

    IFS=$'\n' echo "${messCapacities[@]}" dfdf

    # List of paths of all the userDetails.txt files
    readarray userfiles < <(find "$location" -name 'userDetails.txt')

    # The rollnos. of students who have filed their preferences
    readarray filed < <(grep -o -E '[0-9]{9}' mess.txt)

    # We rely on grep to have outputted the rollnos. in order
    for rollno in ${filed[@]}; do

        # As the deletion command at the end of this loop
        # removes any duplicates, we must ensure that the
        # current rollno. was not removed for this reason
        [[ -z "$(grep -o -E '[0-9]{9}' mess.txt)" ]] && continue

        # Find the user file corresponding to the roll no.
        userfile=$(grep "$rollno" ${userfiles[@]} | cut -f1 -d:)

        pref=$(sed -nE 's/Mess Pref: ([0-9]+)/\1/p' "$userfile")

        if [[ ${messCapacities[pref]} -gt 0 ]]; then
            # Allocate mess
            ((messCapacities[pref]-=1))
            # update student's userDetails.txt
            sed -E 's/(Mess:).*/\1 '"${pref}/" "$userfile" > "$tempfile"
            cat "$tempfile" > "$userfile"
        fi
        # Remove the roll no. from mess.txt
        sed -i "s/${rollno}//" "$messtxt"
    done

    # Update the mess capacities in the file
    for ((i=1;i<"${#messCapacities[@]}";i++)); do
        sed -Ei "$(($i+1))"',/Student Preferences/ s/([0-9]+) [0-9]+/\1 '"${messCapacities[i]}/" "$messtxt"
    done



# If user is an inmate (heh, inmates), file preference
elif [[ $(id -nG) =~ 'inmates' ]]; then 

    # Mess pref should be given as argument
    { [[ -n "$1" ]] && [[ "$1" != 'help' ]]; } && pref=$1 || {
        echo 'Usage: messAllocation mess_number';
        exit 1;
    }

    # update userDetails.txt
    userfile=${HOME}/userDetails.txt
    sed -Ei 's/(Mess Pref: ).*/\1'"${pref}/" "$userfile"

    # update mess.txt
    echo $(sed -nE 's/Roll no\.: ([0-9]+)/\1/p' "$userfile") >> "$messtxt"

fi

rm -f "$tempfile"