table_to_csv.sh: Convert a space-delimited table (where the last column may contain spaces) to CSV (comma separated value)

ps.console

$ ps -f | tee /dev/stderr | ./table_to_csv > ps.csv
UID        PID  PPID  C STIME TTY          TIME CMD
martin   12310  3022  0 09:36 pts/13   00:00:00 /bin/bash
martin   13255 12310  0 10:18 pts/13   00:00:00 ps -f
martin   13256 12310  0 10:18 pts/13   00:00:00 tee /dev/stderr
martin   13257 12310  0 10:18 pts/13   00:00:00 /bin/bash ./table_to_csv

ps.csv

table_to_csv

#!/bin/bash
# Convert a space-delimited table (where the last column may contain spaces)
# to CSV (comma separated value).

# Usage: ps -eF | ./table_to_csv

# Example:
# ps -f | tee '/tmp/the script and the CSV handles non-word characters: \ " , *' | ./table_to_csv
# "UID","PID","PPID","C","STIME","TTY","TIME","CMD"
# "martin","12310","3022","0","09:36","pts/13","00:00:00","/bin/bash"
# "martin","13320","12310","0","10:24","pts/13","00:00:00","ps -f"
# "martin","13321","12310","0","10:24","pts/13","00:00:00","tee /tmp/the script and the CSV handles non-word characters: \ "" , *"
# "martin","13322","12310","0","10:24","pts/13","00:00:00","/bin/bash ./table_to_csv"

Q='"' # to escape " as ""
while read -r LINE; do
    read -r -a FIELDS <<< "$LINE" # split words into array

    # Detect the number of columns, based on the fact that
    # there are at least 2 columns and
    # the first line does not contain spaces in the last column
    if (( LASTCOL == 0 )); then
        LASTCOL=$((${#FIELDS[@]} - 1))
    fi

    for I in "${!FIELDS[@]}"; do # indices of FIELDS
        if (( I == LASTCOL )); then break; fi
        printf '"%s",' "${FIELDS[$I]/$Q/$Q$Q}"
    done
    LAST="${FIELDS[*]:$LASTCOL}" # array slice
    printf '"%s"\n' "${LAST/$Q/$Q$Q}"
done

# For sanity in shell scripting, shellcheck table_to_csv
# See https://www.shellcheck.net/ 

Why not implement this in a scripting language with a more sane syntax and better string+CSV libraries, say Ruby?

The intent here is to call ps ... | table_to_csv often while avoiding the Ruby startup time+space penalty, thus resorting to extreme Bash.