How to list packages needing update in format for `yum update-to`

Question

How can I get a space-separated list of the packages with pending updates on CentOS7 in the format that is required for passing as an argument to the yum update-to command?

I want to update all the packages on my production server running CentOS7. Before I update them on production, I want to update them on staging and verify that the changes don't break our server's applications. After validation, we'll schedule a change ticket for production and run that same/vetted yum update-to command (as opposed to the potentially non-deterministic & non-idempotent yum update command) on production at a later date.

So I'm trying to [a] determine all the packages that have an update available for them on my server and [b] prepare a command using yum update-to that will list exactly the packages and their versions to be updated.

Here's an example of the yum update-to command's required syntax:

yum update-to dbus-1.10.24-13.el7_6 dbus-libs-1.10.24-13.el7_6 java-1.8.0-openjdk-1.8.0.242.b08-1.el7 java-1.8.0-openjdk-headless-1.8.0.242.b08-1.el7 tzdata-java-2019c-1.el7 unzip-6.0-21.el7

The problem is that yum update --assumeno and yum list updates both output the list of packages in a totally distinct format than what yum update-to expects.

Here's an example of the above commands' output related to the packages in the example above:

[root@cent7 ~]# yum update --assumeno | grep -E 'dbus|java|unzip'
---> Package dbus.x86_64 1:1.6.12-17.el7 will be updated
---> Package dbus.x86_64 1:1.10.24-13.el7_6 will be an update
---> Package dbus-libs.x86_64 1:1.6.12-17.el7 will be updated
---> Package dbus-libs.x86_64 1:1.10.24-13.el7_6 will be an update
---> Package java-1.8.0-openjdk.x86_64 1:1.8.0.181-3.b13.el7_5 will be updated
---> Package java-1.8.0-openjdk.x86_64 1:1.8.0.242.b08-1.el7 will be an update
--> Processing Dependency: gtk2(x86-64) for package: 1:java-1.8.0-openjdk-1.8.0.242.b08-1.el7.x86_64
---> Package java-1.8.0-openjdk-headless.x86_64 1:1.8.0.181-3.b13.el7_5 will be updated
---> Package java-1.8.0-openjdk-headless.x86_64 1:1.8.0.242.b08-1.el7 will be an update
--> Processing Dependency: pcsc-lite-libs(x86-64) for package: 1:java-1.8.0-openjdk-headless-1.8.0.242.b08-1.el7.x86_64
--> Processing Dependency: cups-libs(x86-64) for package: 1:java-1.8.0-openjdk-headless-1.8.0.242.b08-1.el7.x86_64
---> Package tzdata-java.noarch 0:2017b-1.el7 will be updated
---> Package tzdata-java.noarch 0:2019c-1.el7 will be an update
---> Package unzip.x86_64 0:6.0-16.el7 will be updated
---> Package unzip.x86_64 0:6.0-21.el7 will be an update
 dbus                     x86_64 1:1.10.24-13.el7_6              base     245 k
 dbus-libs                x86_64 1:1.10.24-13.el7_6              base     169 k
 java-1.8.0-openjdk       x86_64 1:1.8.0.242.b08-1.el7           base     293 k
 java-1.8.0-openjdk-headless
 tzdata-java              noarch 2019c-1.el7                     base     187 k
 unzip                    x86_64 6.0-21.el7                      base     171 k
[root@cent7 ~]# 
[root@cent7 ~]# yum list updates | grep -E 'dbus|java|unzip'
dbus.x86_64                           1:1.10.24-13.el7_6                base    
dbus-libs.x86_64                      1:1.10.24-13.el7_6                base    
java-1.8.0-openjdk.x86_64             1:1.8.0.242.b08-1.el7             base    
java-1.8.0-openjdk-headless.x86_64    1:1.8.0.242.b08-1.el7             base    
tzdata-java.noarch                    2019c-1.el7                       base    
unzip.x86_64                          6.0-21.el7                        base    
[root@cent7 ~]# 

How do I get translate the output of the packages and their versions from yum update --assumeno or yum list updates into a format that is accepted by yum update-to?

Answer 1

This solution with sed and awk works:

[root@cent7 ~]# pkgs=`yum -q list updates 2>&1 | tail -n+2 | awk '{print $1 "|" $2}' | sed 's/\.[^.]*|\(.*\:\)*/-/' | tr "\n" " "`
[root@cent7 ~]# echo "yum update-to $pkgs"
yum update-to dbus-1.10.24-13.el7_6 dbus-libs-1.10.24-13.el7_6 java-1.8.0-openjdk-1.8.0.242.b08-1.el7 java-1.8.0-openjdk-headless-1.8.0.242.b08-1.el7 tzdata-java-2019c-1.el7 unzip-6.0-21.el7 
[root@cent7 ~]# 

But I hope someone can come up with a better solution that's less of a hack. Ideally the solution would be one that tells yum to output the format in a more batch-friendly format.