Bash scripting 14 – Generating data files

Issue 249, May 2025 of Linux Magazine, p52-55, had an article on using awk, and gnu plot to manipulate data. In order to try and make use of this, and learn more, I am trying to figure out how to write a csv file.

Write 10 lines to the first column should be in sequence e.g. 1-10 and the 2nd column should be random numbers. This should be written to a file.

So after some digging I managed to come up with this, by modifying some existing solutions

write_csv(){
    echo \"$1\",\"$2\" > log.csv # write to file, use >> to append
}

#sources of help
echo "number" "data" # for reference, not written to file 
for ((i = 0 ; i < 10 ; i++)); do
    echo $i, $RANDOM # echo to screen (stdout)
	echo $i, $RANDOM >> log.csv # write to file
    #write_csv $(($i, $RANDOM % 10))
done

The screen output for me was

number data
0, 17109
1, 2872
2, 22572
3, 7228
4, 27923
5, 6335
6, 20004
7, 32343
8, 10005
9, 21905

While the file output (log.csv) was similar but without the headings, which I just put in for my own reference, the file does work as a csv as I can open in LibreOffice Calc.

0, 17109
1, 2872
2, 22572
3, 7228
4, 27923
5, 6335
6, 20004
7, 32343
8, 10005
9, 21905

As the numbers are quite big, a closer examination, promoted me to make the following modification

echo $i, $((RANDOM % 20)) # echo to screen (stdout)
echo $i, $((RANDOM % 20)) >> log.csv # write to file

This fixes the 2nd column to produce a number between 1 and 20.

number data
0, 17
1, 12
2, 12
3, 16
4, 2
5, 13
6, 10
7, 6
8, 16
9, 16
cat log.csv
0, 3
1, 17
2, 8
3, 16
4, 10
5, 18
6, 5
7, 14
8, 11
9, 11

The script was called gencsv1.sh, which as expected needed execute permissions

chmod +x gencsv.sh

References

In order to help me I used the following, so giving credit to these sources as would be expected.

• https://stackoverflow.com/questions/40175868/how-to-create-csv-file-using-shell-script
• https://stackoverflow.com/questions/1194882/how-to-generate-random-number-in-bash
• https://linuxhandbook.com/bash-loops/

Tags

#Bash,#Bashscripting,#Files,#Random,#Data,#CSV,