Obtenir des détails sur un package avant de l'installer?

Lorsque je tape "mc" sur mon terminal Ubuntu 14.04, j'obtiens un

The program 'mc' is currently not installed. You can install it by typing:
sudo apt-get install mc

Comment puis-je obtenir des détails sur le programme «mc» avant de l'installer? Je veux confirmer que c'est bien le fichier que je veux, et pas un autre.

Le moyen le plus rapide est d'utiliser un terminal apt-cacheet un peu de confiance ;)

apt-cache show mc

Package: mc
Priority: optional
Section: universe/utils
Installed-Size: 1434
Maintainer: Ubuntu Developers <[email protected]>
Original-Maintainer: Debian MC Packaging Group <[email protected]>
Architecture: amd64
Version: 3:4.8.13-3
Provides: mcedit
Depends: e2fslibs (>= 1.37), libc6 (>= 2.15), libglib2.0-0 (>= 2.35.9), libgpm2 (>= 1.20.4), libslang2 (>= 2.2.4), libssh2-1 (>= 1.2.5), mc-data (= 3:4.8.13-3)
Recommends: mime-support, perl, unzip
Suggests: arj, bzip2, catdvi | texlive-binaries, dbview, djvulibre-bin, file, genisoimage, gv, imagemagick, links | w3m | lynx, odt2txt, poppler-utils, python, python-boto, python-tz, xpdf | pdf-viewer, zip
Filename: pool/universe/m/mc/mc_4.8.13-3_amd64.deb
Size: 464160
MD5sum: 8bb8f947d50bcba2f68d2b66a66963c1
SHA1: c61ad7e5581ee46619069c0435c54be5e1fc34c7
SHA256: 21557289003bd195ff5a0212a00365067c5d15f0f9767556512c09da96a012d5
Description-en: Midnight Commander - a powerful file manager
 GNU Midnight Commander is a text-mode full-screen file manager. It
 uses a two panel interface and a subshell for command execution. It
 includes an internal editor with syntax highlighting and an internal
 viewer with support for binary files. Also included is Virtual
 Filesystem (VFS), that allows files on remote systems (e.g. FTP, SSH
 servers) and files inside archives to be manipulated like real files.
Description-md5: 252a5c5aeeb7425db45357d4ab8aa55f
Homepage: http://www.midnight-commander.org
Bugs: https://bugs.launchpad.net/ubuntu/+filebug
Origin: Ubuntu

une autre possibilité est aptitude, mais vous devez généralement les installer en premier:

sudo apt-get install aptitude

Et afficher les informations sur le package avec aptitude show aptitude

Package: aptitude                        
State: installed
Automatically installed: no
Multi-Arch: foreign
Version: 0.6.11-1ubuntu3
Priority: optional
Section: admin
Maintainer: Ubuntu Developers <[email protected]>
Architecture: amd64
Uncompressed Size: 4.990 k
Depends: aptitude-common (= 0.6.11-1ubuntu3), libapt-pkg4.12 (>= 0.9.16), libboost-iostreams1.55.0, libc6 (>= 2.14), libcwidget3, libgcc1 (>= 1:4.1.1), libncursesw5 (>= 5.6+20070908), libsigc++-2.0-0c2a (>= 2.2.0), libsqlite3-0 (>=
         3.6.5), libstdc++6 (>= 4.9), libtinfo5, libxapian22
Recommends: aptitude-doc-en | aptitude-doc, sensible-utils, libparse-debianchangelog-perl
Suggests: tasksel, debtags, apt-xapian-index
Conflicts: aptitude
Provides: aptitude
Provided by: aptitude
Description: terminal-based package manager
 aptitude is a package manager with a number of useful features, including: a mutt-like syntax for matching packages in a flexible manner, dselect-like persistence of user actions, the ability to retrieve and display the Debian
 changelog of most packages, and a command-line mode similar to that of apt-get. 

 aptitude is also Y2K-compliant, non-fattening, naturally cleansing, and housebroken.
Homepage: http://aptitude.alioth.debian.org/

En utilisant l'interface graphique, vous pouvez ouvrir "Ubuntu Software Center" et rechercher mcou Midnight Commander.

Il vous donnera une description complète du paquet. Il est également utile si vous ne connaissez pas le nom exact du package.

Vous pouvez également installer Synaptic et y effectuer une recherche similaire.

Le logiciel peut également être installé dans le Centre logiciel ou Synaptic sans utiliser la ligne de commande.

Il existe de nombreuses façons de procéder. Le plus simple par défaut est apt-cache search.

apt-cache search <regex>

Cela vous donnera quelque chose comme ceci:

$ apt-cache search cheese
cheese - tool to take pictures and videos from your webcam
gir1.2-cheese-3.0 - tool to take pictures and videos from your webcam - gir bindings
libcheese-dev - tool to take pictures and videos from your webcam - base dev
libcheese-doc - tool to take pictures and videos from your webcam - documentation
libcheese-gtk-dev - tool to take pictures and videos from your webcam - widgets dev
libcheese-gtk23 - tool to take pictures and videos from your webcam - widgets
libcheese7 - tool to take pictures and videos from your webcam - base library
cheese-common - Common files for the Cheese tool to take pictures and videos
python-pyip - Python modules for raw ip packet assembling/disassembling

Cela équivaut en quelque sorte à:

dpkg-query -Wf '${Package} ${binary:Summary}\n'

Sauf que cela dpkg-queryne semble fonctionner que sur les choses que vous avez déjà installées.

apt lista une recherche globale (plutôt que regex) qui est un peu plus naturelle pour la plupart des utilisateurs mais vous ne pouvez pas (encore) modifier le format de sortie. Cependant, après avoir regardé la source , vous pouvez sortir le résumé:

$ apt list -o 'APT::Cmd::List-Include-Summary=1'  *cheese* 
Listing... Done
cheese/trusty 3.10.2-0ubuntu2 amd64
  tool to take pictures and videos from your webcam

cheese-common/trusty 3.10.2-0ubuntu2 all
  Common files for the Cheese tool to take pictures and videos

gir1.2-cheese-3.0/trusty 3.10.2-0ubuntu2 amd64
  tool to take pictures and videos from your webcam - gir bindings

libcheese-dev/trusty 3.10.2-0ubuntu2 amd64
  tool to take pictures and videos from your webcam - base dev

libcheese-doc/trusty 3.10.2-0ubuntu2 all
  tool to take pictures and videos from your webcam - documentation

libcheese-gtk-dev/trusty 3.10.2-0ubuntu2 amd64
  tool to take pictures and videos from your webcam - widgets dev

libcheese-gtk23/trusty 3.10.2-0ubuntu2 amd64
  tool to take pictures and videos from your webcam - widgets

libcheese7/trusty 3.10.2-0ubuntu2 amd64
  tool to take pictures and videos from your webcam - base library

C'est un peu compliqué avec l'argument option, mais vous pouvez alias cela assez facilement si vous l'aimez.

Et aptitudepeut aussi aider:

$ aptitude search cheese
p   cheese                                                                       - tool to take pictures and videos from your webcam                                     
p   cheese:i386                                                                  - tool to take pictures and videos from your webcam                                     
p   cheese-common                                                                - Common files for the Cheese tool to take pictures and videos                          
v   cheese-common:i386                                                           -                                                                                       
p   gir1.2-cheese-3.0                                                            - tool to take pictures and videos from your webcam - gir bindings                      
p   gir1.2-cheese-3.0:i386                                                       - tool to take pictures and videos from your webcam - gir bindings                      
p   libcheese-dev                                                                - tool to take pictures and videos from your webcam - base dev                          
p   libcheese-dev:i386                                                           - tool to take pictures and videos from your webcam - base dev                          
p   libcheese-doc                                                                - tool to take pictures and videos from your webcam - documentation                     
p   libcheese-gtk-dev                                                            - tool to take pictures and videos from your webcam - widgets dev                       
p   libcheese-gtk-dev:i386                                                       - tool to take pictures and videos from your webcam - widgets dev                       
p   libcheese-gtk23                                                              - tool to take pictures and videos from your webcam - widgets                           
p   libcheese-gtk23:i386                                                         - tool to take pictures and videos from your webcam - widgets                           
p   libcheese7                                                                   - tool to take pictures and videos from your webcam - base library                      
p   libcheese7:i386                                                              - tool to take pictures and videos from your webcam - base library