Month: May 2016

What It Is Like To Be a Programmer

This is the most realistic video of what it is to be a programmer that I have ever seen. They read the docs and the source a majority of the time in order to be able to write what they are writing. This is rarely demonstrated when I hear people describe programming to new or would-be programmers.

jq Is the grep, sed and awk for json

The only problem with jq is that its not installed by default in ubuntu or ubuntu-server. Its not in the default ubuntu-cloudimg. One must apt-get install jq.

https://stedolan.github.io/jq/manual/ says, “jq is a lightweight and flexible command-line JSON processor.”

In working with juju, we work with json formatted cookies in a ~/.go-cookies file. Sometimes we need to investigate these cookies to develop, verify, and debug our services.

An unexpired cookie value might be as good as a password or authentication token and so for the purpose of our debugging sometimes everything but the value is good enough. The jq filter ‘.[]|del(.Value)‘ strips all of the .Value properties from every object in the input array. This results in:

{
“Name”: “macaroon-a40e7abc65a78faf130dc652d45052c1c8b5b4aeff8181f44a15175b6525558f”,
“Domain”: “api.staging.example.com”,
“Path”: “/identity/”,
“Secure”: false,
“HttpOnly”: false,
“Persistent”: true,
“HostOnly”: true,
“Expires”: “2016-05-09T19:52:21Z”,
“Creation”: “2016-04-11T15:52:21.466266522-04:00”,
“LastAccess”: “2016-04-11T15:52:21.928768825-04:00”,
“Updated”: “2016-04-11T15:52:21.928768825-04:00”,
“CanonicalHost”: “api.staging.example.com”
}
{
“Name”: “macaroon-a605d07b7a95ba7e57a267ed507f673bce1188d0de7f544074f1c33ec4a8ff2a”,
“Domain”: “www.example.org”,
“Path”: “/identity/”,
“Secure”: false,
“HttpOnly”: false,
“Persistent”: true,
“HostOnly”: true,
“Expires”: “2016-05-03T21:46:35Z”,
“Creation”: “2016-04-05T17:46:36.351842179-04:00”,
“LastAccess”: “2016-05-02T15:11:10.525298848-04:00”,
“Updated”: “2016-04-05T17:46:36.351842179-04:00”,
“CanonicalHost”: “www.example.org”
}
{
“Name”: “macaroon-authn”,
“Domain”: “www.example.org”,
“Path”: “/NEENR/”,
“Secure”: false,
“HttpOnly”: false,
“Persistent”: true,
“HostOnly”: true,
“Expires”: “2016-05-03T19:11:09.794240373Z”,
“Creation”: “2016-05-02T15:11:10.592852105-04:00”,
“LastAccess”: “2016-05-02T15:23:26.813664654-04:00”,
“Updated”: “2016-05-02T15:11:10.592852105-04:00”,
“CanonicalHost”: “www.example.org”
}

Now lets say you want to remove the cookie with the Path value “/NEENR/”.

The jq filter: ‘.[] | select(.Path!=”/NEENR/”)’ does that job.

These examples show filter and map, but what about reduce?

Min, max, min_by and max_by are nice default reducers.

  • min_by(.Expires) shows the next expiring cookie.
  • max_by(.Created) shows the most recently created cookie.
  • [.[]|.Expires]|max if you don’t care about the rest of the cookie and just want the max date.
  • [.[]|.Expires]|min if you just want the min date.

See the Array Construction section of the manual for the details on the syntax. I like to think of it as the .[]|.NAME returns elements and if I want them in an array I wrap it in [] for array construction.

jq is a sweet tool that I’m glad to have in my toolbox.