How can I create a multi-column html table in bash?

Although it would certainly be possible to modify your existing code to accomplish this task, I chose to refactor it instead using methods I am a bit more familiar with than awk.

An added feature of the method I used is that an empty cell will be automatically added for players with an odd number of teams.

First, from your example, I assume you would have a file named "Player 1teams.list" with the follow text:

Team 1
Team 2
Team 3
Team 4

Here is my proposed solution, commented and optimized for readability:

#!/bin/bash

# Array of players
PLAYERS=("Player 1")

# Loop through players array
for PLAYER in "${PLAYERS[@]}"; do

    # Echo the table header row for the current player
    echo "<tr>"
    echo "  <th colspan=2>${PLAYER}</th>"
    echo "</tr>"

    # Reset the TEAMS array on each loop (reuse the array for each player)
    TEAMS=()

    # Read each line of the teams file for the current player
    while IFS= read -r LINE || [[ -n "$LINE" ]]; do
        # Store the current player's teams in an array
        TEAMS+=("$LINE")
    done < "${PLAYER}teams.list"

    # Calculate the array key for the last line of the file
    # (array keys are used for line numbers, so they start at 0 instead of 1)
    LASTLINE="$(( ${#TEAMS[@]} - 1 ))"

    # Loop through teams for the current player
    for LINE in "${!TEAMS[@]}"; do

        # If the current line number is even, we are starting a table row
        if [ "$(( LINE % 2 ))" -eq 0 ]; then
            echo "<tr>"
            echo "  <td>${TEAMS[$LINE]}</td>"

            # If an even line is the last line of the file, add a blank cell
            if [ "$LINE" == "$LASTLINE" ]; then
                echo "  <td></td>"
                echo "</tr>"
            fi

        # If the current line number is odd, we are ending a table row
        else
            echo "  <td>${TEAMS[$LINE]}</td>"
            echo "</tr>"
        fi
    done
done

Here is a condensed version of the the above code:

#!/bin/bash

# Array of players
PLAYERS=("Player 1")

for PLAYER in "${PLAYERS[@]}"; do
    echo -e "<tr>\n  <th colspan=2>${PLAYER}</th>\n</tr>"
    TEAMS=(); while IFS= read -r LINE || [[ -n "$LINE" ]]; do TEAMS+=("$LINE"); done < "${PLAYER}teams.list"
    LASTLINE="$(( ${#TEAMS[@]} - 1 ))"
    for LINE in "${!TEAMS[@]}"; do
        if [ "$(( LINE % 2 ))" -eq 0 ]; then
            echo -e "<tr>\n  <td>${TEAMS[$LINE]}</td>"
            if [ "$LINE" == "$LASTLINE" ]; then echo -e "  <td></td>\n</tr>"; fi
        else
            echo -e "  <td>${TEAMS[$LINE]}</td>\n</tr>"
        fi
    done
done

Edit: I have posted a new answer using the awk code you provided as well

You can do this with an if statement which checks for even/odd numbered rows:

for ((i=0; i<${#PLAYERS[@]}; ++i)); do
    awk -F '\n' -v NAME="${PLAYERS[i]}" 'BEGIN {print "<tr>\n  <th colspan="2">" NAME "</th>\n</tr>"} \
    {if (NR%2==1) {print "<tr>\n  <td>"$0"</td>"} else {print "  <td>"$0"</td>\n</tr>"}}
    END {if (NR%2==1) {print "</tr>"}}' \
    "${PLAYERS[i]}teams.list"
done

The if statement checks that the current line is odd using the formula NR%2==1 (line number modulo 2 is equal to 1), then prints the appropriate html for that table row.

I also made the following code changes :

• Removed the for loop, as awk already loops through each line of the file
• Removed "<" file redirection, as awk already expects a filename as the last parameter
• Joined multiple print statements using \n newline characters

Note: I posted this as a separate answer, as I had completely rewritten your code in my original post.