NAME

augprint - create an idempotent augtool script for a given file

SYNOPSIS

augprint [--pretty|-p] [--regexp[=n]|-r[n]] [--noseq|-s] [--verbose|-v] [--lens name|-l name] [--target /target|-t /target] FILE

DESCRIPTION

augprint creates an augtool script for a given FILE consisting primarily of "set" commands.
The resulting augtool script is designed to be idempotent, and will not result in any changes when applied to the original file.
augprint replaces each numbered location in the tree with a path-expression that uniquely identifies the position using the values within that position.
This makes the path-expression independant of the position-number, and thereby applicable to files which in which the same data may exist at an alternate position-number
See "Examples" for sample output

Regexp output

By default augprint produces path-expressions made up of simple equality "=" comparisions 
  set /files/etc/hosts/seq::*[ipaddr='127.0.0.1']/ipaddr '127.0.0.1'
The option --regexp changes the output to produce regular expression comparisions 
  set /files/etc/hosts/seq::*[ipaddr=~regexp('127\\.0\\..*')]/ipaddr '127.0.0.1'
The minimum length N of the regular expression can be specified using "--regexp=N"
augprint will choose a longer regular expression than N if multiple values would match using the N character regular expression.

Limitations

Append-only
The output is based primarily on set operations. The set operation can only:
a) change an existing value in-situ
b) append a new value after the last position in the group
This means that when an entry is re-created, it may not be in the same position as originally intended. ie if the entry for 192.0.2.3 does not already exist, it will be created as the last entry in /etc/hosts
Often, such out-of-sequence entries will not matter to the resulting configuration file. If it does matter, further manual editing of the "augtool" script will be required.
Repeated Values
augprint is not always successful in finding a path-expression which is unique to a position. In this case augprint appends a position to an expression which is not unique
This occurs in particular if there are repeated values within the file.
For an /etc/hosts file of 
  #------
  192.0.2.3   defaultdns
  #------
augprint would produce the output 
  set /files/etc/hosts/#comment[.='--------'][1] '--------'
  set /files/etc/hosts/seq::*[ipaddr='192.0.2.3']/ipaddr '192.0.2.3'
  set /files/etc/hosts/seq::*[ipaddr='192.0.2.3']/canonical 'defaultdns'
  set /files/etc/hosts/#comment[.='--------'][2] '--------'
Notice how "#comment" paths have "[1]" and "[2]" appended respectively to the "[expr]"
Other paths which do have unique path-expressions are not directly affected

OPTIONS

-v, --verbose
Include the original numbered paths as comments in the output
-p, --pretty
Create more readable output by adding spaces and empty lines
-r, -rN, --regexp, --regexp= N
Generate regular expressions to match values, using a minumum length of N characters from the value N can be omitted and defaults to 8
-l, --lens=LENS
Use LENS for the given file; without this option, augprint uses the default lens for the file
-t targetfile, --target=targetfile
Generate the script for the FILE specified as if its path was really targetfile This will apply the lens corresponding to targetfile to FILE and modifying the resulting path-expressions of FILE to correspond to targetfile targetfile must be the full path name, starting with a '/' See "Examples" for how --target can be used in practice
-s, --noseq
Do not use "seq::*" in the output, use "*" instead. For example 
  set /files/etc/hosts/*[ipaddr='127.0.0.1']/ipaddr '127.0.0.1'
IMPORTANT: The resulting output will no longer create a new entry for 127.0.0.1 if none already exists. The "--noseq" option exists so that the resulting paths can be used with augeas versions prior to 1.13.0 (subject to this limitation)

EXAMPLES

These examples use the following /etc/hosts file as the FILE 
  127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
  192.0.2.3   dns-a
  192.0.2.4   dns-b
The output from "augtool 'print /files/etc/hosts'" would be 
  /files/etc/hosts
  /files/etc/hosts/1
  /files/etc/hosts/1/ipaddr = "127.0.0.1"
  /files/etc/hosts/1/canonical = "localhost"
  /files/etc/hosts/1/alias[1] = "localhost.localdomain"
  /files/etc/hosts/1/alias[2] = "localhost4"
  /files/etc/hosts/1/alias[3] = "localhost4.localdomain4"
  /files/etc/hosts/2
  /files/etc/hosts/2/ipaddr = "192.0.2.3"
  /files/etc/hosts/2/canonical = "dns-a"
  /files/etc/hosts/3
  /files/etc/hosts/3/ipaddr = "192.0.2.4"
  /files/etc/hosts/3/canonical = "dns-b"

Default output

"augprint /etc/hosts" 
  set /files/etc/hosts/seq::*[ipaddr='127.0.0.1']/ipaddr '127.0.0.1'
  set /files/etc/hosts/seq::*[ipaddr='127.0.0.1']/canonical 'localhost'
  set /files/etc/hosts/seq::*[ipaddr='127.0.0.1']/alias[.='localhost.localdomain'] 'localhost.localdomain'
  set /files/etc/hosts/seq::*[ipaddr='127.0.0.1']/alias[.='localhost4'] 'localhost4'
  set /files/etc/hosts/seq::*[ipaddr='127.0.0.1']/alias[.='localhost4.localdomain4'] 'localhost4.localdomain4'
  set /files/etc/hosts/seq::*[ipaddr='192.0.2.3']/ipaddr '192.0.2.3'
  set /files/etc/hosts/seq::*[ipaddr='192.0.2.3']/canonical 'dns-a'
  set /files/etc/hosts/seq::*[ipaddr='192.0.2.4']/ipaddr '192.0.2.4'
  set /files/etc/hosts/seq::*[ipaddr='192.0.2.4']/canonical 'dns-b'

Verbose output

"augprint --verbose /etc/hosts" 
  #   /files/etc/hosts
  #   /files/etc/hosts/1
  #   /files/etc/hosts/1/ipaddr  '127.0.0.1'
  set /files/etc/hosts/seq::*[ipaddr='127.0.0.1']/ipaddr '127.0.0.1'
  #   /files/etc/hosts/1/canonical  'localhost'
  set /files/etc/hosts/seq::*[ipaddr='127.0.0.1']/canonical 'localhost'
  #   /files/etc/hosts/1/alias[1]  'localhost.localdomain'
  set /files/etc/hosts/seq::*[ipaddr='127.0.0.1']/alias[.='localhost.localdomain'] 'localhost.localdomain'
  ...

Rexexp output

"augprint --regexp=4 /etc/hosts" 
  set /files/etc/hosts/seq::*[ipaddr=~regexp('127\\..*')]/ipaddr '127.0.0.1'
  set /files/etc/hosts/seq::*[ipaddr=~regexp('127\\..*')]/canonical 'localhost'
  set /files/etc/hosts/seq::*[ipaddr=~regexp('127\\..*')]/alias[.=~regexp('localhost\\..*')] 'localhost.localdomain'
  set /files/etc/hosts/seq::*[ipaddr=~regexp('127\\..*')]/alias[.=~regexp('localhost4')] 'localhost4'
  set /files/etc/hosts/seq::*[ipaddr=~regexp('127\\..*')]/alias[.=~regexp('localhost4\\..*')] 'localhost4.localdomain4'
  set /files/etc/hosts/seq::*[ipaddr=~regexp('192\\.0\\.2\\.3')]/ipaddr '192.0.2.3'
  set /files/etc/hosts/seq::*[ipaddr=~regexp('192\\.0\\.2\\.3')]/canonical 'dns-a'
  set /files/etc/hosts/seq::*[ipaddr=~regexp('192\\.0\\.2\\.4')]/ipaddr '192.0.2.4'
  set /files/etc/hosts/seq::*[ipaddr=~regexp('192\\.0\\.2\\.4')]/canonical 'dns-b'
Note that although a minimum length of 4 has been specified, augprint will choose longer regular expressions as needed to ensure a unique match.

Using --lens

If a file is not assocatiated with a lens by default, --lens lensname can be used to specify a lens.
When --lens is specified, the output is prefixed with suitable "transform" and "load-file" statements, as required to complete the augtool script, and a setm statement to exclude other autoloaded lenses.
"augprint --lens shellvars /etc/skel/.bashrc" 
  setm /augeas/load/*[incl='/etc/skel/.bashrc' and label() != 'shellvars']/excl '/etc/skel/.bashrc'
  transform shellvars incl /etc/skel/.bashrc
  load-file /etc/skel/.bashrc
  set /files/etc/skel/.bashrc/#comment[.='.bashrc'] '.bashrc'
  set /files/etc/skel/.bashrc/#comment[.='Source global definitions'] 'Source global definitions'
  set /files/etc/skel/.bashrc/@if[.='[ -f /etc/bashrc ]'] '[ -f /etc/bashrc ]'
  set /files/etc/skel/.bashrc/@if[.='[ -f /etc/bashrc ]']/.source '/etc/bashrc'
  set /files/etc/skel/.bashrc/#comment[.='User specific environment'] 'User specific environment'
  ...
The lenses "simplelines" "shellvars" are most commonly useful as lenses for files that do not have a specific lens

Using --target

In order to prepare an augtool script intended for a given file, it may be desired to copy the file to another location, rather than editting the original file.
The option --target simplifies this process.
a) copy /etc/hosts to a new location 
   cp /etc/hosts ~
b) edit ~/hosts to suit 
   echo '192.0.2.7   defaultdns' >> ~/hosts
c) Run "augprint" as follows 
   augprint --target /etc/hosts ~/hosts
d) Copy the relevant part of the output to an augtool script or other Augeas client 
   set /files/etc/hosts/seq::*[ipaddr='192.0.2.7']/ipaddr '192.0.2.7'
   set /files/etc/hosts/seq::*[ipaddr='192.0.2.7']/canonical 'defaultdns'
Notice that "augprint" has generated paths corresponding to --target (/etc/hosts) instead of the FILE argument (~/hosts)

ENVIRONMENT VARIABLES

AUGEAS_ROOT
The effective file system root, defaults to '/'.
AUGEAS_LENS_LIB
Colon separated list of directories with lenses. Directories specified here are searched before the default directories /usr/share/augeas/lenses and /usr/share/augeas/lenses/dist

EXIT STATUS

The exit status is 0 when the command was successful and 1 if any error occurred.

FILES

Lenses and schema definitions in /usr/share/augeas/lenses and /usr/share/augeas/lenses/dist

AUTHOR

George Hansper <[email protected]> Copyright 2022 George Hansper
Augeas (and augprint) are distributed under the GNU Lesser General Public License (LGPL), version 2.1

SEE ALSO

augtool(1)
Augeas project homepage <https://www.augeas.net/>
Augeas path expressions <https://github.com/hercules-team/augeas/wiki/Path-expressions>

Recommended readings

Pages related to augprint you should read also:
augtool(1)

Questions & Answers

Helpful answers and articles about augprint you may found on these sites:
Stack Overflow Server Fault Super User Unix & Linux Ask Ubuntu Network Engineering DevOps Raspberry Pi Webmasters Google Search