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,
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