APT – Redirecting apt and apt-get Commands

aptbashcommand linepackage-management

When sudo apt-get install -y blender redirects to /dev/null , the installing process completed without any warnings or errors.

But when sudo apt install -y blender redirects to /dev/null , this warning is shown :

WARNING: apt does not have a stable CLI interface. Use with caution in scripts.

So what's difference between apt-get and apt commands that cause this warning ?

I know that it's better to use apt instead of apt-get, but how to redirect the apt output without this warning ?

Is there another way to make apt less noisy ? (beacause -q and -qq options are not silently as they be should)

Best Answer

If you are redirecting the output in order not to see it at all, then you can ignore the warning. It's intended to tell you that if you want to read the output later as a log, you can expect clearer information if you use apt-get, since some of the dynamic output from apt is not captured accurately.

Apparently APT is smart enough to realise you are redirecting its output but not to understand where you are sending it.

If you need to you can always read the logged output, by the way; it's automatically saved in /var/log/apt/term.log (and compressed and rotated when it gets old).

Related Solutions

How to Compile GnuPG from Source – Step-by-Step Guide

I have found the provided speedo method the easiest for gnupg-2.1.X:

sudo apt-get update
sudo apt-get install libldap2-dev gtk+-2 libbz2-dev
after unpacking the latest gnupg-2.1.X tarball and cd to the new folder, run the command:
```
sudo make -f build-aux/speedo.mk native INSTALL_PREFIX=/usr/local
```
sudo ldconfig
download the latest pinentry-0.9.5, run ./configure && make && sudo make install.
test it out: gpg2 --version

****I would like to update this answer for GnuPG v2.2.x. The following bash file will install on Ubuntu 16.04, 17.10:

cd ~/Downloads
version=gnupg-2.2.2
wget https://gnupg.org/ftp/gcrypt/gnupg/$version.tar.bz2
wget https://gnupg.org/ftp/gcrypt/gnupg/$version.tar.bz2.sig
tar xf $version.tar.bz2
cd $version
sudo apt-get update
sudo apt-get install -y libldap2-dev
sudo apt-get install -y gtk+-2
sudo apt-get install -y rng-tools
sudo apt-get install -y libbz2-dev
sudo apt-get install -y zlib1g-dev
sudo apt-get install -y libgmp-dev
sudo apt-get install -y nettle-dev
sudo apt-get install -y libgnutls28-dev
sudo apt-get install -y libsqlite3-dev
sudo apt-get install -y adns-tools
sudo apt-get install -y libreadline-dev
sudo apt-get install -y pinentry-gtk2
sudo apt-get install -y pcscd scdaemon
sudo make -f build-aux/speedo.mk native INSTALL_PREFIX=/usr/local
sudo ldconfig

This will support TOFU and Smart Cards like Yubikey 4 Nano. To update to the newest version edit version=gnupg-2.2.2 Test it: gpg --version

APT – Resolving ‘Unstable CLI Interface’ Warning

apt is for the terminal and gives beautiful output while apt-get and apt-cache are for scripts and give stable, parsable output. The script equivalent of your apt show command therefore is:

apt-cache show $PACKAGE_NAME >pack_info.txt

Now to answer your questions one by one:

What do we exactly mean by Stable CLI Interface?

apt's output is not well usable in scripts. For example, apt install (compared to apt-get install) displays a progress bar that's useless for scripts and can throw errors when the output is parsed. apt show firefox shows a hint for an additional record, which is also totally useless in a script, you want it to simply output every record there – that's what apt-cache show firefox does. Let's see what man apt has to say about that:

The apt(8) commandline is designed as an end-user tool and it may change behavior between versions. While it tries not to break backward compatibility this is not guaranteed either if a change seems beneficial for interactive use.

All features of apt(8) are available in dedicated APT tools like apt-get(8) and apt-cache(8) as well. apt(8) just changes the default value of some options (see apt.conf(5) and specifically the Binary scope). So you should prefer using these commands (potentially with some additional options enabled) in your scripts as they keep backward compatibility as much as possible.

How to safely and error-free use such commands in scripts?

Just use apt-get or apt-cache respectively instead of plain apt. :) See this answer for a list of equivalents.

Is there a way to only and only redirect STDOUT of apt show to a file?

You did that correctly already: >file or 1>file redirects stdout, 2>file redirects stderr and &>file redirects both to file.

Best Answer

Related Solutions

How to Compile GnuPG from Source – Step-by-Step Guide

APT – Resolving ‘Unstable CLI Interface’ Warning

Related Question