[pacman-dev] [PATCH] checkupdates: Add package download mode with "-d"

[Chris Down]

This new mode, which must be run as root, allows for the precaching of
packages which can then subsequently be updated by calling
"pacman -Syu" as normal. This can then be integrated with a cron script
(for example, checkupdates-cron[0]) for automated, safe downloading of
packages alongside getting the list of packages to update, or run
manually on the command line to download new packages, but avoid
updating the main package database.

As a side effect of adding the -d option, argument handling (which was
previously not present) is now done using "getopts". This seems like a
reasonable way to do it instead of just hacking in a check for "-d" as
$1 now, but I'm not particularly averse to either. "getopts" would just
allow for better future flexibility in this area.

It is possible to do this as another script, say, downloadupdates, but
we would encounter pretty heavy code duplication with "checkupdates", so
it seems more sensible to do it here.

Due to the use of --noconfirm, this has some limitations when we
encounter more complex upgrade scenarios, for example when a new package
conflict occurs, an upgrade path cannot be correctly/automatically
determined, a package was replaced, etc. This is not a major problem --
in the worst case, we just don't get the packages that we wanted
downloaded and an error message is displayed to the user.

The choice to hide both STDOUT and STDERR of "pacman -Syuw" is
potentially up for debate. It makes it more difficult to determine where
the problem was if the command fails -- we still display a message
saying that that was the case, and set the exit code accordingly, but
the actual cause needs to be determined by the user elsewhere. For this
reason, "-p" exists to force the package download to output as normal.

It seems desirable that "-p" also affects the silence of the database
update, but this is also up for discussion if people feel it should not
be within the remit of the (( silent )) checks.

[0]: https://github.com/cdown/checkupdates-cron
---
 contrib/checkupdates.sh.in | 44 +++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 41 insertions(+), 3 deletions(-)

diff --git a/contrib/checkupdates.sh.in b/contrib/checkupdates.sh.in
index 413b78a..4a74632 100644
--- a/contrib/checkupdates.sh.in
+++ b/contrib/checkupdates.sh.in
@@ -21,16 +21,46 @@
 declare -r myname='checkupdates'
 declare -r myver='@PACKAGE_VERSION@'
 
-if (( $# > 0 )); then
+download=0
+silent=1
+
+usage() {
 	echo "${myname} (pacman) v${myver}"
 	echo
 	echo "Safely print a list of pending updates"
 	echo
 	echo "Usage: ${myname}"
 	echo
+	echo "Options:"
+	echo "  -d  Download upgradeable packages to pacman package cache."
+	echo "  -p  Print pacman output from the database upgrade and package download."
+	echo
 	echo 'Note: Export the "CHECKUPDATES_DB" variable to change the path of the temporary database.'
 	exit 0
-fi
+}
+
+run_silent() {
+	{
+		(( silent )) && exec &>/dev/null
+		"$@"
+	}
+}
+
+
+while getopts ':dp' opt; do
+	case $opt in
+		d)
+			if (( UID )); then
+				echo "Download mode can only be run as root." >&2
+				exit 2
+			fi
+
+			download=1
+		;;
+		p) silent=0 ;;
+		\?) usage ;;
+	esac
+done
 
 if [[ -z $CHECKUPDATES_DB ]]; then
 	CHECKUPDATES_DB="${TMPDIR:-/tmp}/checkup-db-${USER}/"
@@ -43,9 +73,17 @@ eval $(awk -F' *= *' '$1 ~ /DBPath/ { print $1 "=" $2 }' @sysconfdir@/pacman.con
 
 mkdir -p "$CHECKUPDATES_DB"
 ln -s "${DBPath}/local" "$CHECKUPDATES_DB" &> /dev/null
-fakeroot pacman -Sy --dbpath "$CHECKUPDATES_DB" --logfile /dev/null &> /dev/null
+run_silent fakeroot pacman -Sy --dbpath "$CHECKUPDATES_DB" --logfile /dev/null
 pacman -Qqu --dbpath "$CHECKUPDATES_DB" 2> /dev/null
 
+if (( download )); then
+	if ! run_silent pacman -Suw --noconfirm --dbpath "$CHECKUPDATES_DB"; then
+		ret=$?
+		(( silent )) && echo "Failed to download packages." >&2
+		exit "$ret"
+	fi
+fi
+
 exit 0
 
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