mjhjmtu

I use Ubuntu 16.04 with Nginx and Bash. I know that it's not possible to directly pipe data into zip.

For example, if you host websites on Apache/Nginx webserver, this command set would fail after filling in the password:

drt="/var/www/html"
mysqldump -u root -p --all-databases | zip "$drt/db-$date.zip"

What will be your workaround if you really desire the end file to be a zip file?

If you really want to use zip, you can use Jeff Schaller’s trick:

drt="/var/www/html"
mysqldump -u root -p --all-databases | zip "$drt/db-$date.zip" -

This will create a ZIP file containing a file named - whose contents are the database dump. This is mentioned in the zip manpage:

zip also accepts a single dash ("-") as the name of a file to be compressed, in which case it will read the file from standard
input, allowing zip to take input from another program. For example:

tar cf - . | zip backup -

You could also use /dev/stdin instead:

mysqldump -u root -p --all-databases | zip -FI "$drt/db-$date.zip" /dev/stdin

This would result in an archive containing a file named dev/stdin which might be harder to handle properly. - is a common short-hand to tell programs to use standard input or output; it’s not something that the shell handles, it has to be supported by each individual program.

In both cases you’d probably want to use funzip to extract the data; it extracts the first member of an archive to its standard output.

If you are open to alternative compression tools, try this almost identical alternative.

drt="/var/www/html"
mysqldump -u root -p --all-databases | gzip >"$drt/db-$date.gz"

If you prefer you can substitute gzip with bzip2 or xz, and the typical extension from gz to bz2 or xz.

If you really prefer a zip file over using gzip or tar:

drt="/var/www/html"
scratch="$(mktemp)"
if mysqldump -u root -p --all-databases > "$scratch"; then
 zip "$drt/db-$date.zip" "$scratch"
fi
rm -f "$scratch"

Optionally, you can use a temporary directory to have a more useful filename:

drt="/var/www/html"
scratchdir="$(mktemp -d)"
if mysqldump -u root -p --all-databases > "$scratchdir/db-$date.sql"; then
 zip -j "$drt/db-$date.zip" "$scratchdir/db-$date.sql"
fi
rm -rf "$scratchdir"