/usr/share/doc/command-not-found/README.md is in command-not-found 18.04.4.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 | # Command-not-found
This application implements the command-not-found spec at:
https://wiki.ubuntu.com/CommandNotFoundMagic
If you want automatic prompts to install the package, set
COMMAND_NOT_FOUND_INSTALL_PROMPT in your environment.
To use it in bash, please add the following line to your .bashrc file:
. /etc/bash_command_not_found
To use it in zsh, please add the following line to your .zshrc file:
. /etc/zsh_command_not_found
Note that it overrides the preexec and precmd functions, in case you have
defined your own.
## Data sources
Command-not-found will for the following data sources:
1. sqlite3 DB in /usr/share/command-not-found/commands.db, if that is
*not* found it will fallback to (2)
2. legacy /usr/share/command-not-found/programs.d/*.db gdbm style database
The datasource (1) is generated from data found on the archive server
in deb822 format. The data is generated via
https://code.launchpad.net/~mvo/command-not-found-extractor/+git/command-not-found-extractor
and is downloaded via `apt update`.
The datasource (2) is generated via a static `command-not-found-data`
deb package. It is less rich and dynamic than (1) and should be
considered legacy and only be used if no better data source is
available.
### DB schemas
#### Legacy DB:
Simple key/value store with key `program_name` (e.g. bash) and value a
comma separated list of packages that provide the program name. The
filename indicates the component and architecuture via:
`$component-$arch.db`.
#### Sqlite3 DB:
The database looks like this:
```
CREATE TABLE IF NOT EXISTS "commands"
(
[command] TEXT PRIMARY KEY NOT NULL,
[pkgID] INTEGER NOT NULL,
FOREIGN KEY ([pkgID]) REFERENCES "pkgs" ([pkgID])
);
CREATE TABLE IF NOT EXISTS "packages"
(
[pkgID] INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL,
[name] TEXT,
[version] TEXT,
[priority] INTEGER
);
```
There is no need to store the component because we do not display that
in c-n-f. Note that the "name" in the "pkgs" table may include an
architecture qualifier. This is an optimization for multi-arch
systems, by default if there is "bash:amd64" and "bash:i386" on an
amd64 multi-arch systems we will not store "bash:i386" in the DB at
all and will store "bash:amd64" just as "bash". However for commands
that are only available for the foreign arch (e.g. "wine:i386") the
full qualified package name is stored in the DB and used in the c-n-f
output.
## Development
To run the tests type:
$ python -m unittest discover
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