awk -F "," '{print $1 }' inputfile1.txt | sort -u > distinctOutput.txt

--compress-program=PROG
          compress temporaries with PROG; decompress them with PROG -d
   -T, --temporary-directory=DIR
          use  DIR  for temporaries, not $TMPDIR or /tmp; multiple options
          specify multiple directories

base64 < /dev/urandom | sort

21877 root      20   0   11.1m   0.6m   0.5m R  63.9  0.0   7:23.46 base64
21878 root      20   0   21.4m   8.2m   0.8m R  31.9  0.4   4:44.15 sort

$ ls /tmp/sort* | head
/tmp/sort03IIcQ
/tmp/sort052vXK
/tmp/sort07ZCcO
/tmp/sort09yrTN
/tmp/sort0anX08
/tmp/sort0BruPR
/tmp/sort0EgCYY
/tmp/sort0GsbQs
/tmp/sort0hCMDD
/tmp/sort0hdSMT
$ ls /tmp | grep -c sort
1990

real    0m5.134s
user    0m5.048s
sys     0m0.080s

real    0m6.006s
user    0m5.836s
sys     0m0.152s

real    0m17.937s
user    0m17.565s
sys     0m0.348s