Monday, 4 May 2020

Functions in aliases for bash



Thought i'd share a little nugget.

So i do a few commands in linux that are repetitive in nature, so i often alias them out so i'm lazy and don't have to type as much.
For instance, one of my repetitive commands is `git grep`, which is a great tool for going through your git repo to search those reg expressions.
So in my ~/.bashrc, i have
alias ggrep="git grep"
Now, all i do is ggrep <my search>

Something i learn't today however, is passing an argument to an alias.
My work has a lot of test boxes scattered around connected to different gear, so i ssh a lot to these. since the are all nicely formatted to tb<something a rather>, i decided i would now like to replace ssh tb0933 with tb 0933.
To do this is easy enough, but unlike a standard bash shell, we can't pass in the variable and just access like $x. Instead what we have to do is to create a function, and then call it.
So in the very simple case of the above my command equates to
alias tb='function ssh_tb=() { ssh tb$@; }; ssh_tb'
So expanding on this, we define the function ssh_tb() which when called, will execute the command ssh tb$@, and then at the end of this, we call it.

Easy!

Thursday, 26 March 2020

Linux device trees



Such a great resource at https://source.android.com/devices/architecture/dto/syntax

Thursday, 18 July 2019

Key bindings in linux for spotify



Had issues with my keyboard and the play button not working with spotify... (this was my work one).

So if you're play button is not working with spotify, then try this guys suggestion, http://shkspr.mobi/blog/2011/12/linux-spotify-keybindings/


Sunday, 16 December 2018

Videos not playing in opera on linux


So, it's no secret i've loved opera since the day i first installed it, I think i joined the opera revolution around the 3.62 mark in 1999 apparently! (man i'm old). Anyhow - read up more about the opera history here https://en.wikipedia.org/wiki/History_of_the_Opera_web_browser

Since i'm this fancy new software developer type person,  i have it installed as my browser of choice at work, but we run linux here since the platforms we use are linux as well. I'm not complaining mind you, i like linux too!

But the support for playing videos is lacking :( (wuh waaahhh), I believe this is due to the license with Mpeg's and not being able to distribute the codec with the program.
From this post it appears that Opera doesn't have the rights to distribute the codec with the program. however! Google does (cos they probably have deeper pockets right?)

Anyhow - very easy to fix, we simply copy over the top of the libffmpeg.so that we have in our opera directory with one from the google chromium browser :)

sudo cp /usr/lib/chromium-browser/libffmpeg.so /usr/lib/x86_64-linux-gnu/opera/


Restart the browser and things should be all good again :)


Tuesday, 4 December 2018

Measuring function time in linux using C


Measuring Time 

So in my job recently i had to time how long it took for a module to be plugged in before that module became "ready" ... the answer was 46 seconds.. but some careful polling changes and a change how firmware was loaded mean't that got chopped in half almost to 26 seconds!

But that's not the point, the point was how did i do such timing.

The original way i found was to use to use clock(). Clock returns an approximation of the processor time used by the program.
Using the following code..

#include <time.h>
#include <stdio.h> 
int main() 
{ 
   clock_t start, stop, length; 
   start = clock(); 
   
   function_to_be_time(parameters); 
   
   stop = clock(); 

   length = (double) stop - start / CLOCKS_PER_SEC; 

   printf("Time for your function was %ld\n", length); 
   
   return; 
} 

Now, this works mind you! but there's a gotchya here, oh yes, you saw that coming didn't you.. go on - admit it..
I probably didn't read the manual (RTFM!) for clock properly.... because the times i was getting back for my function calling didn't make sense compared to time stamped outputs!?
Clock() is returning time used by the program... i know - that didn't make sense, but it does if you mention the word threading.
See i was in a multi-threaded enviroment. So while this was timing my function in this "program" (ie thread!) my "program" had been running differently (in time) from other functions (ie threads!) that made up the entired module "ready" process.

Take 2. 

So instead, i used clock_gettime() with CLOCK_MONOTONIC.
This gave me a much better accuracy across my module insertion process, and started giving me numbers that made sense with other time stamped debug statements.

So.. using the following code,
#include <time.h>
#include <stdio.h>

/* Convert the timespec struct into a seconds value
static double TimeToSeconds(struct timespec* ts)
{
   return (double)ts->tv_sec + (double)ts->tv_nsec / 1000000000.0;
}

int main()
{
    struct timespec start, stop;
    double time_spent = 0;
    clock_gettime(CLOCK_MONOTONIC, &start);

    <YOUR FUNCTION GOES HERE>

    clock_gettime(CLOCK_MONOTONIC, &stop);
    time_spent = TimeToSeconds(&stop) - TimeToSeconds(&start);
    
    printf("your function time was %ld\n", time_spent);

    return;
}

Hopefully that helps someone with timing issues in threads etc.. lemme know if it works for you :)

Lastly - so i don't forget (possibly)... time stamping..
I'm just gonna post the code

time_t rawtime;
struct tm * timeinfo;
time ( &rawtime );
timeinfo = localtime ( &rawtime );
printf("Time Stamp is [%d:%d:%d]\n", 
        timeinfo->tm_hour, timeinfo->tm_min, timeinfo->tm_sec);

All good fun :)



Graduated!.... now what.


So you've graduated.... now what.

So that time came and went where i finished up my degree and paraded in front of my family across the stage to shake the mans hand that had never met me and get that piece of paper that now says what i always wanted to say... I'm qualified

Qualified.. I find it strange term. Its a term that says to people you know what we want you to know. But when push comes to shove..... do you?
I think the answer to that is much like the exam post, you go to an interview, the interviewer asks you the questions that we all know the answers too. So i guess... Rope interviewing? hah...

So now i've been released into the real world, to find my place, to make my 'mark' as the educators have instructed us. We have given you all the tools... we have given you the best possible start.
Sometimes it feels like i got shown to the boat, given some wood, nails, hammer and saw, and pushed off while waving goodbye i look down to find all the holes in the bottom now appearing.



Monday, 3 October 2016

Group Assignments, bad learning.



So... taking this great course (INFO263) and we are going learn up to 5 different coding languages... Just a pity that we never really get taught them.

The assignment for this course is worth like 40%, (Woah!), and it's a group assignment (Groan).

I've always thought that group assignments would be great, Really - i did... past tense..
I thought that it was a bit conveyance of what (the uni calls) the real world is all about, after all it's not like we get stuck in the corner at work and told you have 2 hours to complete this task in silence.
No - we work in teams, in groups, in lots of things like that.

However - what the real world has and our "group projects" don't have is a manager.. a boss... el captaino... big honcho .. etc etc...
This makes the real world work better, as when your fellow group member maybe not putting as much effort into the assignment as they oughta be, then in the real world.. the boss gets angry.. then turns green and smashes up the place.
Oh - wait, thats' a different boss...

Anyways - that is my point of difference is, as grumpy as you can get with different members of your group - that's all it is. Grumpiness, they don't care, all of a sudden they get a passing mark for their assignment and they've done diddly squat .. in kiwi speak - that's nothing. literally.

So anyhow - back to the topic. 5 coding languages, HTML, CSS, PHP, MYSQL, Javascript. The lecturer seems to be in his own little world with this tho, because its an INFO course, Majority of students taking it are commerce. Meaning ... it's all about the money money money (admit it - you sang that in your head didn't you).

So when he's showing us javascript on the power point, and saying (and i quote).. "I don't know why you would need all this math stuff on a business website"... its because not everything in this world is related to commerce.. thats why.
There are other reasons why you can use php other than to build a bloody shopping cart.

Anyhow - learn't more in two days of Code Academy (seriously good) than in 5 weeks of lectures, and then to top it off - the exam was all about design or proposing a solution to a website... none of which was done in class.... gah - the horror... the shame..

Anyhow - gotta run to the next class.... later gators!