Execute several command in linux shell file [closed]

I only can get the desire output when I run the command one by one. How can I combine all the command in a shell script and get the desired output?

//insert timestamp column
$ vmstat -n 5 | (while read; do echo "$(date +%Y-%m-%d.%H:%M:%S) $REPLY"; done)> vm.txt
//remove 1st & 2nd row
$ sed '1,2d' vm.txt > vm2.txt
//convert text file to csv
$ sed 's/^ *//;s/ */,/g' vm2.txt > vm2.csv
//insert column name
$ echo $'datetime, r, b, swpd, free, buff, cache, si, so, bi, bo, in, cs, us, sy, id, wa, st' | cat - vm2.csv> chart.csv
$ psql -p 5432 -U postgres -c "copy vmstat FROM '/root/report/chart.csv' delimiter '|' csv header"


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