Getting started with Pequod

Running a script

psh is a normal PiROS command. Give it the path to a script:

bob@pros> psh files/hello.psh

Author scripts with the prano editor (prano files/hello.psh), or push them from your own machine. A script's output goes to the terminal — or, when the script is served by tintin, into the web response.

$who = "world";
echo "hello $who\n";

bob@pros> psh files/hello.psh
hello world

Two kinds of file

Pequod decides how to read a file by a single test: does it contain a <? tag?

• No <? anywhere → the whole file is pure code (like the example above). This is the natural mode for shell scripts.
• Contains <? → the file is a template: text outside the tags is emitted literally, code runs inside. This is how you build web pages.

You rarely think about it — write scripts as plain code, write pages as templates. The web page chapter covers template mode in full.

Variables

Variables start with $. No declaration; assign and use.

$name = "Ada";
$year = 1815;
$active = 1;
echo $name;          // Ada
echo $year + 10;     // 1825

Types

Pequod has three value types:

Strings & interpolation

Both quote styles interpolate $variables. Use \n, \t, \\, and escaped quotes.

$user = "mary";
echo "hi $user\n";      // hi mary
echo 'hi $user\n';      // hi mary  (single quotes interpolate too, in psh)

Concatenate with the dot operator .:

$greeting = "hi, " . $user . "!";
echo $greeting;          // hi, mary!

Operators at a glance

$n = 5;
$n += 3;                 // 8
$n++;                     // 9
echo $n > 10 ? "big" : "small";   // small

Comments

# hash comment (whole line)
// slash comment (whole line)
/* block comment
   over several lines */

Example: a tiny report

Putting the basics together — variables, a loop, arithmetic, and formatted output.

$items  = ["cpu", "disk", "net"];
$counts = [12, 44, 7];
$total  = 0;

for ($i = 0; $i < count($items); $i++) {
    echo $items[$i] . ": " . $counts[$i] . "\n";
    $total += $counts[$i];
}
echo "total: $total\n";

bob@pros> psh files/report.psh
cpu: 12
disk: 44
net: 7
total: 63