parse csv file using gawk

one,two,"three, four",five
"six, seven",eight,"nine"

BEGIN { FS="," }
{
  for (i=1; i<=NF; i++) printf "field #%d: %sn", i, $(i)
  printf "---------------------------n"
}

field #1: one
field #2: two
field #3: "three
field #4:  four"
field #5: five
---------------------------
field #1: "six
field #2:  seven"
field #3: eight
field #4: "nine"
---------------------------

field #1: one
field #2: two
field #3: "three, four"
field #4: five
---------------------------
field #1: "six, seven"
field #2: eight
field #3: "nine"
---------------------------

# csv2delim.awk converts comma delimited files with optional quotes to delim separated file
#     delim can be any characer, defaults to tab
# assumes no repl characters in text, any delim in line converts to repl
#     repl can be any characer, defaults to ~
# changes two consecutive quotes within quotes to '

# usage: gawk -f csv2delim.awk [-v delim=d] [-v repl=`"] input-file > output-file
#   	-v delim	delimiter, defaults to tab
#   	-v repl		relacement char, defaults to ~

# e.g. gawk -v delim=; -v repl=` -f csv2delim.awk test.csv > test.txt

# abe 2-28-7
# abe 8-8-8 1.0 fixed empty fields, added replacment option
# abe 8-27-8 1.1 used split
# abe 8-27-8 1.2 inline rpl and "" = '
# abe 8-27-8 1.3 revert to 1.0 as it is much faster, split most of the time
# abe 8-29-8 1.4 better message if delim present

BEGIN {
    if (delim == "") delim = "t"
    if (repl == "") repl = "~"
    print "csv2delim.awk v.m 1.4 run at " strftime() > "/dev/stderr" ###########################################
}

{
    #if ($0 ~ repl)	{
    #	print "Replacment character " repl " is on line " FNR ":" lineIn ";" > "/dev/stderr"
    #}
    if ($0 ~ delim)	{
    	print "Temp delimitor character " delim " is on line " FNR ":" lineIn ";" > "/dev/stderr"
    	print "    replaced by " repl > "/dev/stderr"
    }
    gsub(delim, repl)

    $0 = gensub(/([^,])""/, "\1'", "g")
#   $0 = gensub(/""([^,])/, "'\1", "g")	# not needed above covers all cases

    out = ""
    #for (i = 1;  i <= length($0);  i++)
    n = length($0)
    for (i = 1;  i <= n;  i++)
    	if ((ch = substr($0, i, 1)) == """)
    		inString = (inString) ? 0 : 1 # toggle inString
    	else
    		out = out ((ch == "," && ! inString) ? delim : ch)
    print out
}

END {
    print NR " records processed from " FILENAME " at " strftime() > "/dev/stderr"
}

"first","second","third"
"fir,st","second","third"
"first","sec""ond","third"
" first ",sec   ond,"third"
"first" , "second","th  ird"
"first","sec;ond","third"
"first","second","th;ird"
1,2,3
,2,3
1,2,
,2,
1,,2
1,"2",3
"1",2,"3"
"1",,"3"
1,"",3
"","",""
"","""aiyn","oh"""
"""","""",""""
11,2~2,3

rem test csv2delim
rem default is: -v delim={tab} -v repl=~
gawk                      -f csv2delim.awk test.csv > test.txt
gawk -v delim=;           -f csv2delim.awk test.csv > testd.txt
gawk -v delim=; -v repl=` -f csv2delim.awk test.csv > testdr.txt
gawk            -v repl=` -f csv2delim.awk test.csv > testr.txt

BEGIN { FS="," }
{
  for (i=1; i<=NF; i++) {
    f[++n] = $i
    if (substr(f[n],1,1)==""") {
      while (substr(f[n], length(f[n]))!=""" || substr(f[n], length(f[n])-1, 1)=="\") {
        f[n] = sprintf("%s,%s", f[n], $(++i))
      }
    }
  }
  for (i=1; i<=n; i++) printf "field #%d: %sn", i, f[i]
  print "----------------------------------n"
}