Appending to files

Let's start with a simple question: how to append content to an existing file?

The answer is: check the "help" for the io.writeFile* function you need. Most of them already support an extra parameter to append to existing files.

io.writeFileString example

To write to a custom log you would do something like:

io.writeFileString("mylog.log", new Date() + " | Just did something\n");

But using this example the file mylog.log would get overwritten every time you execute it. To get around it simple add an extra flag:

io.writeFileString("mylog.log", new Date() + " | Just did something\n", void 0, true);

And everytime you run it, it will add a new line to the mylog.log file.

Appending several files into one

A one_liner that is usually helpfull is:

> $from(io.listFilenames("my/path")).ends(".js").select(r => { io.writeFileString("all.js", io.readFileString(r), void 0, true); });

This will actually create all.js file with the contents of all files in my/path with suffix ".js". Of course you now can change the $from conditions to whatever special conditions you might have.

Test latency

The usual latency test most of us use if simply execute the ping operating system command from the source to the target we want to measure. But nowadays, ICMP packets (what ping really transmits) might be blocked by a firewall or similar.

With OpenAF's function ow.format.testLatency that isn't a problem since it will try to open a TCP socket to the desired host and port and measure the time taken for the socket connection to be created (and then it closes it).

It's not perfect but is usually enough to understand the relative latency to another host and port.

First I will present a test function a later show how to use it as an one-liner.

The test function

Here is a test function that will taken several measures and return you: each measure, the average and a chart representation of the variation between each measure.

ow.loadFormat();

var tl = (host, port, times) => { 
    times = _$(times).isNumber().default(3); 
    var tries = [], sum = 0, max = 0; 

    for(var ii = 0; ii < times; ii++) {
        tries.push({
            sample: ii+1, 
            latency: ow.format.testPortLatency(host, port)
        });
    }; 
    tries.forEach((v) => {
        sum += v.latency; 
        max = (v.latency > max) ? v.latency : max; 
        v.chart = ow.format.string.progress(v.latency, max, 0, 50, "=", " ");
    }); 
    tries.push({ 
        sample: "avg", 
        latency: Math.floor(sum/times) + "ms"
    });

    return tries;
}

The one-liner

Now convert it to a one-liner and write on an openaf-console, for example:

> ow.loadFormat();
> var tl = (host, port, times) => { times = _$(times).isNumber().default(3);var tries = [], sum = 0, max = 0; for(var ii = 0; ii < times; ii++) { tries.push({ sample: ii+1, latency: ow.format.testPortLatency(host, port)});}; tries.forEach((v) => { sum += v.latency; max = (v.latency > max) ? v.latency : max; v.chart = ow.format.string.progress(v.latency, max, 0, 50, "=", " "); }); tries.push({ sample: "avg", latency: Math.floor(sum/times) + "ms" }); return tries; }

And test it:

> table tl("www.yahoo.com", 443);
sample|latency|                      chart                       
------+-------+--------------------------------------------------
1     |63     |==================================================
2     |60     |================================================  
3     |63     |==================================================
avg   |62ms   

Of course, the chart would only help you when there are slight or significant variations in latency between tests:

> table tl("dynamodb.ap-southeast-2.amazonaws.com", 443, 15);
sample|latency|                      chart                       
------+-------+--------------------------------------------------
1     |354    |==================================================
2     |364    |==================================================
3     |357    |================================================= 
4     |351    |================================================  
5     |352    |================================================  
6     |357    |================================================= 
7     |406    |==================================================
8     |358    |============================================      
9     |354    |============================================      
10    |348    |===========================================       
11    |361    |============================================      
12    |358    |============================================      
13    |369    |=============================================     
14    |354    |============================================      
15    |366    |=============================================     
avg   |360ms  

From the command-line

If you want to run it from the command-line:

$ openaf -c 'ow.loadFormat();var tl = (host, port, times) => { times = _$(times).isNumber().default(3);var tries = [], sum = 0, max = 0; for(var ii = 0; ii < times; ii++) { tries.push({ sample: ii+1, latency: ow.format.testPortLatency(host, port)});}; tries.forEach((v) => { sum += v.latency; max = (v.latency > max) ? v.latency : max; v.chart = ow.format.string.progress(v.latency, max, 0, 50, "=", " "); }); tries.push({ sample: "avg", latency: Math.floor(sum/times) + "ms" }); return tries; }; print(printTable(tl(  "www.google.com", 443, 15)));'
sample|latency|                      chart                       
------+-------+--------------------------------------------------
1     |35     |==================================================
2     |30     |===========================================       
3     |30     |===========================================       
4     |26     |=====================================             
5     |30     |===========================================       
6     |29     |=========================================         
7     |29     |=========================================         
8     |28     |========================================          
9     |28     |========================================          
10    |29     |=========================================         
11    |33     |===============================================   
12    |30     |===========================================       
13    |32     |==============================================    
14    |33     |===============================================   
15    |33     |===============================================   
avg   |30ms   

And replace the function arguments on the end of the one-liner.

Quickly validate a YAML file

One of the cons of using YAML (e.g. and any other identation based languages) is forgetting about a tab or a wrong spacing that leads to errors. For example:

jobs:
  #-------------------
  - name: Hello World!
  exec: print('Hello World!')

todo:
  - Hello World!

The problem with this YAML file is on the 4th line since the 3rd line started a map as part of the jobs array but the 4th line is a map entry. One way to quickly check this is using another "one-liner":

$ openaf -i script -e "io.readFileYAML('aYAMLFile.yaml')"

In this case the result would be:

Error while executing operation: YAMLException: bad indentation of a mapping entry at line 4, column 3:
      exec: print('Hello World!')
      ^ (js-yaml_js#1)

Solving the issue:

jobs:
  #-------------------
  - name: Hello World!
    exec: print('Hello World!')

todo:
  - Hello World!

Executing the same one-liner now the result is no errors:

$ openaf -i script -e "io.readFileYAML('aYAMLFile.yaml')"
$

oJob one-liners

On the article Micro remote HTTP file browser we described a fast way to build a micro HTTP server serving files from the current folder. But some (myself included) need faster ways to do it instead of creating an oJob file and executing it.

So doing the same thing on one line that you can just copy+paste whenever you need can be very pratical. But you will be sacrifying readability by anyone else and you. Since oJobs can be used in YAML or JSON this enables you to build a YAML oJob file and then convert it to JSON string where initilization parameters can be easily change. Additionally you can convert back to YAML very easily.

Example

Let's use the micro remote HTTP file browser example. Since YAML provides some features that JSON doesn't (like anchors) the original YAML needs some adaptation:

httpd.yaml

init:
  port: 8080
  path: "."
  uri : "/"

ojob:
  daemon    : true
  sequential: true
  opacks    :
    - oJob-common

include:
  - oJobHTTPd.yaml

todo:
  - name: Init
  - name: HTTP Start Server
    args: "({ port: global.init.port, mapLibs: true })"
  - name: HTTP File Browse
    args: "({ port: global.init.port, path: global.init.path, uri: global.init.uri })"

jobs:
  # ----------
  - name: Init
    exec: "global.init = args.init;"

Convert to a JSON one-liner

Then to convert this YAML file into a JSON string use openaf-console and execute:

> print(stringify(io.readFileYAML("httpd.yaml"), void 0, ""))

{"init":{"port":8080,"path":".","uri":"/"},"ojob":{"daemon":true,"sequential":true,"opacks":["oJob-common"]},"include":["oJobHTTPd.yaml"],"todo":[{"name":"Init"},{"name":"HTTP Start Server","args":"({ port: global.init.port, mapLibs: true })"},{"name":"HTTP File Browse","args":"({ port: global.init.port, path: global.init.path, uri: global.init.uri })"}],"jobs":[{"name":"Init","exec":"global.init = args.init;"}]}

Use the JSON one-liner

Then to use this JSON as an one-liner:

> oJobRun( /* one-liner begin */  {"init":{"port":8080,"path":".","uri":"/"},"ojob":{"daemon":true,"sequential":true,"opacks":["oJob-common"]},"include":["oJobHTTPd.yaml"],"todo":[{"name":"Init"},{"name":"HTTP Start Server","args":"({ port: global.init.port, mapLibs: true })"},{"name":"HTTP File Browse","args":"({ port: global.init.port, path: global.init.path, uri: global.init.uri })"}],"jobs":[{"name":"Init","exec":"global.init = args.init;"}]}  /* one-liner end */ );

To stop just hit "Ctrl-C".

Making changes

If you need to change the folder, port or uri used it's easy to just direclty change on the first init map:

{"init":{"port":8080,"path":".","uri":"/"},

To convert it back to YAML:

io.writeFileYAML("httpd.yaml", /* one-liner begin */  {"init":{"port":8080,"path":".","uri":"/"},"ojob":{"daemon":true,"sequential":true,"opacks":["oJob-common"]},"include":["oJobHTTPd.yaml"],"todo":[{"name":"Init"},{"name":"HTTP Start Server","args":"({ port: global.init.port, mapLibs: true })"},{"name":"HTTP File Browse","args":"({ port: global.init.port, path: global.init.path, uri: global.init.uri })"}],"jobs":[{"name":"Init","exec":"global.init = args.init;"}]}  /* one-line end */ );

Note: since you lose comments we would recommed you to just use the original YAML file.