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doc: Some basic usage and cleanup

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Mattias Wadman 2021-09-18 19:27:46 +02:00
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47
README.md
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@ -14,42 +14,43 @@ $ fq . file.mp3 
* |until 0xd19.7 (end) (599) | |
| | | footers: [0]
 
<b># Show ID3v2 APIC frame</b> 
$ fq '.headers[].frames[] | select(.id == "APIC")' file.mp3 
|00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|0123456789abcdef|.headers[0].frames[1]: {}
0x020| 41 50 49 43 | APIC | id: "APIC" (Attached picture)
0x020| 00 00 15 0c | .... | size: 2700
0x020| 00 00 | .. | flags: {}
0x020| 03 | . | text_encoding: UTF-8 (3)
0x020| 69 6d| im| mime_type: "image/png"
0x030|61 67 65 2f 70 6e 67 00 |age/png. |
0x030| 00 | . | picture_type: 0
0x030| 00 | . | description: ""
0x030| 89 50 4e 47 0d 0a| .PNG..| picture: {} (png)
0x040|1a 0a 00 00 00 0d 49 48 44 52 00 00 01 40 00 00|......IHDR...@..|
* |until 0xab8.7 (2687) | |
<b># Show ID3v2 tag in mp3 file</b> 
$ fq '.headers[0]' file.mp3 
|00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|0123456789abcdef|.headers[0]: {} (id3v2)
0x000|49 44 33 |ID3 | magic: "ID3" (Correct)
0x000| 04 | . | version: 4
0x000| 00 | . | revision: 0
0x000| 00 | . | flags: {}
0x000| 00 00 15 39 | ...9 | size: 2745
0x000| 54 53 53 45 00 00| TSSE..| frames: [2]
0x010|00 0f 00 00 03 4c 61 76 66 35 38 2e 37 36 2e 31|.....Lavf58.76.1|
* |until 0xab8.7 (2735) | |
0xab0| 00 00 00 00 00 00 00| .......| padding: Correct (none) (zero padding)
0xac0|00 00 00 |... |
 
<b># Resolution of embedded PNG file</b> 
$ fq '.headers[].frames[] | select(.id == "APIC").picture.chunks[] | select(.type == "IHDR") | {width, height}' file.mp3 
<b># Resolution of ID3v2 cover art</b> 
$ fq '.headers[0].frames[] | select(.id == "APIC").picture.chunks[] | select(.type == "IHDR") | {width, height}' file.mp3 
{
"height": 240,
"width": 320
}
 
<b># Extract PNG file</b> 
<b># Extract image file</b> 
$ fq '.headers[].frames[] | select(.id == "APIC")?.picture | tobits' file.mp3 > file.png 
$ file file.png 
file.png: PNG image data, 320 x 240, 8-bit/color RGB, non-interlaced
 
<b># Codecs in a mp4 file</b> 
$ fq '[.. | select(.type == "stsd")?.boxes[].type]' file.mp4 
[
"avc1",
"mp4a"
]
</pre>
</sub>
## Goals
- Make structured binary data accessible using the jq language.
- Nested format decoding and bit-oriented decoding.
- Quick cli tool that tries to mimic jq as much as possible.
**NOTE** fq is early in development and many things are missing, broken or do not make sense. This also means there is much opportunity to help out!
## Install
Download archive from [releases](https://github.com/wader/fq/releases) page for your

44
doc/usage.md
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@ -1,3 +1,42 @@
### Basic usage
fq tries to behave the same as jq as much as possible, so you can do:
```sh
fq . test.mp3
fq < test.mp3
fq . < test.mp3
fq . *.png *.jpg
```
### Interactive REPL
fq has an interactive REPL with auto completion and nested REPL support:
```sh
# start REPL with null input
fq -i
# same as
fq -ni
# start REPL with one file as input
fq -i . test.mp3
```
In the REPL you will see a prompt indicating current input and you can type jq expression to evaluate.
```sh
# basic arithmetics
mp3> 1+1
2
# "." is the identity function, returns current input, the mp3 file.
mp3> .
# access the first frame in the mp3 file
mp3> .frames[0]
# start a new REPl with first frame as input
mp3> .frames[0] | repl
```
Use Ctrl-C exits REPL. Ctrl-C interupts current evaluation.
### Arguments
<pre sh>
@ -33,11 +72,6 @@ Usage: fq [OPTIONS] [--] [EXPR] [FILE...]
- TODO: stdin/stdout
### Interactive REPL
- TODO: tab completion, ctrl-d, ctrl-d, help
- TODO: nested, nested with generator
### Script
- TODO: #!