curl-trace-parser
v0.0.10
Published
Parse curl --trace option output to raw HTTP message
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The curl --trace
parser
The story
Did you know that you can record raw HTTP communication of Curl command-line tool with the --trace
and --trace-ascii
option? It's the only way I know to get raw HTTP communication without using the tcpdump
or wireshark
.
For example, this trick is very useful for the proper introspection into HTTP communication of an undocumented RESTful API.
The only glitch is that cURL --trace
saves data in its custom format, far from human-friendly, saving chunks as they are being received and splitting them by packets. If you want a human readable form then this parser is what you need. Delivered as a Node.js package.
Usage
$ curl --trace - http://httpbin.org/ip | curl-trace-parser
Sample API
We will be using this sample API created with the Apiary.io mock server to demonstrate tracing an HTTP communication and the use of the cURL trace parser.
Install the cURL trace parser
$ npm install -g curl-trace-parser
Record your first trace file
$ curl --trace tracefile --header "Content-Type: application/json" \
--request POST \
--data-binary "{ \"product\":\"1AB23ORM\", \"quantity\": 2 }" \
"http://curltraceparser.apiary.io/shopping-cart"
Note this cURL example is copied and pasted from Apiary interactive API documentation.
Examples
--raw
format
The output is ASCII representation of a raw HTTP message with few modifications:
- Request line begins with
>
- Response line begins with
<
- Request and Response is delimited by CR+LF
- Both Request and Response are terminated by an extra trailing LF
Note: This is little bit tricky because HTTP RFC does not have declared delimiter for Request and Response, for obvious reasons.
$ cat tracefile | curl-trace-parser --raw
> POST /shopping-cart HTTP/1.1
> User-Agent: curl/7.24.0 (x86_64-apple-darwin12.0) libcurl/7.24.0 OpenSSL/0.9.8x zlib/1.2.5
> Host: curltraceparser.apiary.io
> Accept: */*
> Content-Type: application/json
> Content-Length: 39
>
> { "product":"1AB23ORM", "quantity": 2 }
< HTTP/1.1 201 Created
< Content-Type: application/json
< Date: Tue, 30 Jul 2013 11:32:30 GMT
< X-Apiary-Ratelimit-Limit: 120
< X-Apiary-Ratelimit-Remaining: 119
< Content-Length: 50
< Connection: keep-alive
<
< { "status": "created", "url": "/shopping-cart/2" }
--blueprint
format
The output is HTTP Request and Response in the API blueprint format which is the superset of markdown.
$ cat tracefile | ./bin/curl-trace-parser --blueprint
# POST /shopping-cart
+ Request
+ Headers
User-Agent:curl/7.24.0 (x86_64-apple-darwin12.0) libcurl/7.24.0 OpenSSL/0.9.8x zlib/1.2.5
Host:curltraceparser.apiary.io
Accept:*/*
Content-Type:application/json
Content-Length:39
+ Body
{ "product":"1AB23ORM", "quantity": 2 }
+ Response 201
+ Headers
Content-Type:application/json
Date:Tue, 30 Jul 2013 11:32:30 GMT
X-Apiary-Ratelimit-Limit:120
X-Apiary-Ratelimit-Remaining:119
Content-Length:50
Connection:keep-alive
+ Body
{ "status": "created", "url": "/shopping-cart/2" }
Note: This format does not expect any CR+LF in the message body
Parse the trace to raw HTTP file using Node.JS
var fs = require('fs');
var parser = require('curl-trace-parser');
fs.readFile('./tracefile', 'utf8', function (err,trace) {
console.log(parser.parse(trace));
})
Output format reverse parser
var fs = require('fs');
var parser = require('curl-trace-parser');
fs.readFile('./tracefile', 'utf8', function (err,trace) {
console.log(parser.parseBack(trace));
})
API Reference
parse(traceString)
- parse string with trace to object with raw request and response
parseToString(traceString)
- parse string with trace to output format
parseBack(outputString)
- parse string with output format back to object with raw request an resposne