I'll assume most readers understand how to place a block or blocks in a world with a command. However, If you send chat /setblock 123 123 123 minecraft:stained_glass 2 replace ; a magenta stained glass block will be placed at 123 123 123. If you use relative coordinates, it's located by an offset of a selector.

/setblock 123 123 123 minecraft:stained_glass 2 replace is a command that a redstoner might use in a command block to create a structure. Even more useful in building is the ability to make the coordinates relative when taking a placed block and reverse engineering it into a command. Relative means related to an entity (e.g. @p ~ ~2 ~ is 2 blocks above "relative" the nearest player).

When working on a map or redstone, it's convenient to be able to get the string for a command as a setblock command. It's really useful when you are building a redstone machine with large numbers of command blocks. The tag data in block is hard to extract and manipulate in a mass of hundreds.

Blockdump reverse engineers a placed block into a setblock command. If there was a command_block to say hello at -370 67 956, you should get...

/setblock -370 67 956 minecraft:command_block 5 replace
{conditionMet:1,auto:0,CustomName:"@",powered:1,Command:"say
hello",x:-370,y:67,z:956,id:"Control",SuccessCount:1,TrackOutput:1}

The Idea : that a new command "blockdump" dumps (reverse engineers) an area of the map to a command setblock format, including the NBT tags to a file. This command simplifies the ability of the user to write command blocks so that the mapper can see the commands and blocks they've placed as text.

I originally thought this was an extension of the executefile command (a prior suggestion), but really it's a separate idea. It's a type of clone command to a text file that writes the block information as a report, setblock file or execute command file.

The command would work as follows.

/blockdump <type of output> <coords> <file>

The output types are ExFile, File and Report.

/blockdump ExFile|File|Report x1 y1 z1 x2 y2 z2 saveto.txt simply writes out the blocks of the area as setblock commands to a file.

Different options would allow the user to select relative locations to the player or entity. The command would also support absolute locations and the ability to preface with either location type with execute. Such a command would make mapping and redstoning much easier as the user now has reverse engineering of placed blocks into commands.

On options : "File" writes placed blocks into setblocks directly as commands. "ExFile" writes placed blocks as setblocks with a relative offset and prefixed with the "execute command" relative to a player entity. "Report" writes a formatted report about blocks to a file for easy reading. I have implemented a noair option in the mod that skips blocks with minecraft:air.

Output for "File" might be ....

/setblock -368 66 956 minecraft:cobblestone 0 replace 
/setblock -368 66 957 minecraft:cobblestone 0 replace 
/setblock -368 66 958 minecraft:cobblestone 0 replace 
/setblock -368 67 956 minecraft:redstone_wire 15 replace 
/setblock -368 67 957 minecraft:prismarine 0 replace 
/setblock -368 67 958 minecraft:cobblestone 0 replace 
/setblock -368 68 957 minecraft:redstone_wire 14 replace 
/setblock -368 68 958 minecraft:cobblestone 0 replace 
/setblock -368 69 958 minecraft:cobblestone 0 replace 
/setblock -368 70 958 minecraft:cobblestone 0 replace 

The above would be in a file called "saveto.txt".

This would also include command blocks and structure blocks.

/setblock -370 67 956 minecraft:command_block 5 replace {conditionMet:1,auto:0,CustomName:"@",powered:1,Command:"say hello",x:-370,y:67,z:956,id:"Control",SuccessCount:1,TrackOutput:1}

And in execute format for command block command

/execute @p ~ ~ ~ setblock ~-3 ~-1 ~3 minecraft:cobblestone 0 replace 
/execute @p ~ ~ ~ setblock ~-3 ~0 ~1 minecraft:command_block 5 replace {conditionMet:1,auto:0,CustomName:"@",powered:1,Command:"say hello",x:-370,y:67,z:956,id:"Control",SuccessCount:1,TrackOutput:1}

Also from the original (point and click from Lepakko's ) concept reports can be generated.

BlockID: minecraft:chest(54)
Block name: tile.chest = Chest
XYZ: -364 67 956
Metadata: 2
NBT: {x:-364,y:67,z:956,Items:[],id:"Chest",Lock:""}

BlockID: minecraft:cobblestone(4)
Block name: tile.stonebrick = Cobblestone
XYZ: -364 67 958
Metadata: 0

Those that use forge can try the BlockDumpMod for 1.9 to 1.10.2 to test the suggestion http://minecraft.curseforge.com/projects/commandrunnermod/files . I'm thinking also about EntityDump as a suggestion.

You can place the command setblocks with "executefile", a prior suggestion. BTW Note that in "executefile" large dumps run very slowly for now.

Performance is vastly improved by setting logging of admin chat and commandfeedback false

Testing with the following.

section.caleb

/execute @p ~ ~ ~ fill ~-3 ~-1 ~1 ~ ~-1 ~-7 minecraft:stone 4
/execute @p ~ ~ ~ fill ~-2 ~ ~2 ~ ~2 ~2 minecraft:stained_glass 8
/execute @p ~ ~ ~ fill ~-3 ~ ~1 ~-3 ~2 ~1 minecraft:stone 3
/execute @p ~ ~ ~ fill ~-3 ~3 ~2 ~ ~3 ~2 minecraft:log 11

/execute @p ~ ~ ~ tp @p ~-4 ~ ~ 

 and floor.caleb

/execute @p ~ ~ ~ executefile File section.caleb byline rotateeast repeatn 10 cascade
/execute @p ~ ~ ~ executefile File section.caleb byline rotatenorth repeatn 10 cascade
/execute @p ~ ~ ~ executefile File section.caleb byline rotatewest repeatn 10 cascade
/execute @p ~ ~ ~ executefile File section.caleb byline rotatesouth repeatn 10 cascade

Sample

# Hi, this sample.caleb file is a simple building with 2 floors an opening and a chest
# it's used in city1.caleb
# always use /execute format for each line
# comments are # then space
# clear space around me

# Note you can call command block and command blocks can call executefill
# the /execute is optional on each line
@p ~ ~ ~ fill ~5 ~-1 ~5 ~-5 ~10 ~-5 minecraft:air
# build floor
@p ~ ~ ~ fill ~5 ~-1 ~5 ~-5 ~-1 ~-5 minecraft:cobblestone
# walls
@p ~ ~ ~ fill ~5 ~-1 ~-5 ~-5 ~10 ~-5 minecraft:cobblestone
@p ~ ~ ~ fill ~-5 ~-1 ~5 ~-5 ~10 ~-5 minecraft:cobblestone
@p ~ ~ ~ fill ~5 ~-1 ~5 ~5 ~10 ~-5 minecraft:cobblestone
@p ~ ~ ~ fill ~5 ~-1 ~5 ~-5 ~10 ~5 minecraft:cobblestone
# roof
@p ~ ~ ~ fill ~5 ~10 ~5 ~-5 ~10 ~-5 minecraft:cobblestone
# second floor
@p ~ ~ ~ fill ~5 ~5 ~5 ~-5 ~5 ~-5 minecraft:cobblestone
# first floor light
@p ~ ~ ~ fill ~0 ~4 ~0 ~1 ~4 ~1 minecraft:glowstone
@p ~ ~ ~ fill ~0 ~9 ~0 ~1 ~9 ~1 minecraft:glowstone
#opening for door
@p ~ ~ ~ fill ~0 ~0 ~5 ~0 ~1 ~5 minecraft:air

@p ~ ~ ~ fill ~2 ~5 ~1 ~3 ~5 ~-1 minecraft:air
@p ~ ~ ~ fill ~3 ~0 ~3 ~3 ~0 ~3 minecraft:chest
@p ~ ~ ~ fill ~2 ~0 ~-3 ~3 ~0 ~-3 minecraft:stone_stairs 2
@p ~ ~ ~ fill ~2 ~1 ~-2 ~3 ~1 ~-2 minecraft:stone_stairs 2
@p ~ ~ ~ fill ~2 ~2 ~-1 ~3 ~2 ~-1 minecraft:stone_stairs 2
@p ~ ~ ~ fill ~2 ~3 ~0 ~3 ~3 ~0 minecraft:stone_stairs 2
@p ~ ~ ~ fill ~2 ~4 ~1 ~3 ~4 ~1 minecraft:stone_stairs 2
@p ~ ~ ~ fill ~2 ~5 ~2 ~3 ~5 ~2 minecraft:stone_stairs 2

@p ~ ~ ~ setblock ~0 ~0 ~5 minecraft:wooden_door 3
@p ~ ~ ~ setblock ~0 ~1 ~5 minecraft:wooden_door 9
@p ~ ~ ~ setblock ~-1 ~0 ~4 minecraft:prismarine 
@p ~ ~ ~ setblock ~-2 ~0 ~4 minecraft:redstone_lamp 
@p ~ ~ ~ setblock ~-1 ~1 ~4 minecraft:redstone_wire 0 replace
@p ~ ~ ~ setblock ~-1 ~0 ~3 minecraft:redstone_wire 0 replace
@p ~ ~ ~ setblock ~-3 ~0 ~3 minecraft:command_block 5 replace {Command:say hello}

@p ~ ~ ~ setblock ~-2 ~0 ~3 minecraft:lever 13 replace 
# sorry I don't yet rotate nbt tags inside command blocks

This is a command generator for a trefoil know. Many thanks  to MCE30.

import java.io.File;
import java.io.FileNotFoundException;
import java.io.PrintWriter;

public class Mainer {
	static int modelsize = 3;

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		if (args.length > 1) {
			if (args[0].toUpperCase().trim().matches("HELP")) {
				System.out
						.println("Hi, I am a tribute program that creates commandrunnermod samples.");
				System.out.println("Many thanks to MCE30.");
				System.out
						.println("Choose Trefoil, Circle, Staircase and then small,medium,large");
			}
			if (args[1].toUpperCase().trim().matches("SMALL")) {
				modelsize = 2;
			} else if (args[1].toUpperCase().trim().matches("LARGE")) {
				modelsize = 4;
			}

			if (args[0].toUpperCase().trim().matches("TREFOIL")) {
				trefoil(modelsize,
						"trefoil" + new Integer(modelsize).toString()
								+ ".caleb");

			}
		}

	}

	private static void trefoil(int modelsize, String filename) {
		// TODO Auto-generated method stub
		File fl = new File(filename);

		PrintWriter pw = null;
		try {
			pw = new PrintWriter(fl);
		} catch (FileNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		for (double t = 0; t < 2 * 3.14; t = t + .01) {
			double x = (2 + Math.cos(3 * t)) * Math.cos(2 * t);
			double y = (2 + Math.cos(3 * t)) * Math.sin(2 * t);
			double z = Math.sin(3 * t);
			String fromCoord = "~" + Math.round(x * modelsize) + " ~"
					+ Math.round(y * modelsize) + " ~"
					+ Math.round(z * modelsize) + " ";
			String toCoord = "~" + (Math.round(x * modelsize) + 2) + " ~"
					+ (Math.round(y * modelsize) + 2) + " ~"
					+ (Math.round(z * modelsize) + 2) + " ";

			pw.println("/execute @p ~ ~ ~ fill " + fromCoord + toCoord + ""
					+ "minecraft:netherrack");

		}
		pw.close();

	}

}

Big fix. The autocomplete wasn't working .... use executefile in lowercase. Get the July 10th 2016 version.