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https://github.com/shundhammer/ruby-commented-config-file

CommentedConfigFile for Ruby
https://github.com/shundhammer/ruby-commented-config-file

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CommentedConfigFile for Ruby

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# CommentedConfigFile Ruby Class



(c) 2017 Stefan Hundhammer 



License: GPL V2



## Overview



- CommentedConfigFile class

- ColumnConfigFile class

- EtcFstab class

- Generic Diff class for string arrays



This is a Ruby clone of my

[C++ CommentedConfigFile class](https://github.com/shundhammer/commented-config-file).



## System Requirements:



- Ruby 1.9 or later



This class should work on Linux/BSD/Unix-like systems and on all kinds of MS

Windows. It's just some Ruby classes after all.



## CommentedConfigFile



This is a utility class for Ruby to read and write config files that might

contain comments.  This class tries to preserve any existing comments and keep

them together with the content line immediately following them.



This class supports the notion of a header comment block, a footer comment

block, a comment block preceding any content line and a line comment on the

content line itself.



A comment preceding a content line is stored together with the content line,

so moving around entries in the file will keep the comment with the content

line it belongs to.



The default comment marker is '#' like in most Linux config files, but it

can be configured with comment_marker = "...".



## Example



(line numbers added for easier reference)



    001	   # Header comment 1

    002	   # Header comment 2

    003	   # Header comment 3

    004

    005

    006	   # Header comment 4

    007	   # Header comment 5

    008

    009	   # Content line 1 comment 1

    010	   # Content line 1 comment 2

    011	   content line 1

    012	   content line 2

    013

    014	   content line 3

    015

    016	   content line 4

    017	   content line 5 # Line comment 5

    018	   # Content line 6 comment 1

    019

    020	   content line 6 # Line comment 6

    021	   content line 7

    022

    023	   # Footer comment 1

    024	   # Footer comment 2

    025

    026	   # Footer comment 3



Empty lines or lines that have only whitespace belong to the next comment

block: The footer comment consists of lines 022..026.



The only exception is the header comment that stretches from the start of

the file to the last empty line preceding a content line. This is what

separates the header comment from the comment that belongs to the first

content line. In this example, the header comment consists of lines

001..008.



- Content line 1 in line 011 has comments 009..010.

- Content line 2 in line 012 has no comment.

- Content line 3 in line 014 has comment 013 (an empty line).

- Content line 5 in line 017 has a line comment "# Line comment 5".

- Content line 6 in line 020 has comments 018..019 and a line comment.



Applications using this class can largely just ignore all the comment stuff;

the class will handle the comments automagically.



## Sample Output



The `ccf_demo.rb` program in `examples/` produces this output from my `/etc/fstab` file:



    

       1: # /etc/fstab: static file system information.

       2: #

       3: # [sh @ balrog] ~ %  sudo blkid | column -t

       4: #

       5: # /dev/sda1:  LABEL="Win-Boot"    UUID="C6CC71BDCC71A877"                      TYPE="ntfs"

       6: # /dev/sda2:  LABEL="Win-App"     UUID="3E5E77515E770147"                      TYPE="ntfs"

       7: #

       8: # /dev/sdb1:  LABEL="swap"        UUID="be72e905-a417-41a4-a75f-12c0cf774f6a"  TYPE="swap"

       9: # /dev/sdb2:  LABEL="openSUSE"    UUID="1d0bc24c-ae68-4c4e-82af-b3e184b2ac9d"  TYPE="ext4"

      10: # /dev/sdb3:  LABEL="Ubuntu"      UUID="f5c15fbd-0417-4711-a0b7-f66b608bad0c"  TYPE="ext4"

      11: # /dev/sdb5:  LABEL="work"        UUID="7e1d65c8-c6e3-4824-ac1c-c3a4ba90f54f"  TYPE="ext4"

      12: #

      13: #

      14: #                              

      15:

    



    

      Entry #1 content  : /dev/disk/by-label/swap      none             swap  sw                         0  0

      Entry #2 content  : /dev/disk/by-label/openSUSE  /alternate-root  ext4  defaults                   0  2

      Entry #3 content  : /dev/disk/by-label/Ubuntu    /                ext4  errors=remount-ro          0  1

      Entry #4 content  : /dev/disk/by-label/work      /work            ext4  defaults                   0  2



      Entry #5 comment 1:

      Entry #5 comment 2: # Windows disk

      Entry #5 content  : /dev/disk/by-label/Win-Boot  /win/boot        ntfs  defaults,umask=007,gid=46  0  0

      Entry #6 content  : /dev/disk/by-label/Win-App   /win/app         ntfs  defaults,umask=007,gid=46  0  0

    



    

      1:

      2:

      3: # nas:/share/sh              /nas/sh          nfs   bg,intr,soft,retry=6       0  0

      4: # nas:/share/work            /nas/work        nfs   bg,intr,soft,retry=6       0  0

      5:

    



I.e. it correctly detected the header comments, the footer comments and the

comment that belongs to _Entry #5_. When the entries are rearranged, e.g. the

entries for the Windows disk are moved above the Linux disk, that comment

remains attached to that entry, i.e. it is moved together with that entry.



Of course that has limitations. If a comment does not belong to the next entry,

but to the previous one, it is moved to the wrong location. That's life. But

it's much better than throwing away all comments every time a program touches a

config file.



## ColumnConfigFile



This class is derived from CommentedConfigFile. In addition to the comment

handling, this class also manages splitting up column-oriented config files

into the columns.



The content lines may all have the same number of columns (like in

`/etc/fstab`), or they might have different numbers of columns.



## EtcFstab



This class is derived from ColumConfigFile; it handles Linux/Unix /etc/fstab

files. In addition to handling the comments and the columns as the

CommentedConfigFile and ColumConfigFile base classes do, this class gives the

columns a meaning, and it can handle dependencies between mount points

(e.g. you want /var/lib mounted after mounting /var if both are on different

filesystems).



## Diff



This class performs diffs just like the Linux/Unix `diff -u` command.



It operates on string arrays to make it useful in many places where you might

want to get a diff to write it to a log file.