if

conditionally execute statements

<if>   = if <expr> { <statements> } <else>
<else> = ø
       | else <if>
       | else { <statements> }

if evaluates the condition and runs the first statements block, if result is true; otherwise it runs the else part. Condition expression must evaluate to a boolean or null, otherwise if panics.

Syntactically, if is a command and, therefore, can be used in pipelines, redirects and any other places where commands can be used.

check age

if $age >= 18 {
    print "adult"
} else {
    print "not yet adult"
}

check if system has been recently started

# `uptime -r` gives a space-separated list,
# the second value is uptime in seconds
if (uptime -r):spaces[1]:seconds < 2:minutes {
    print "just started"
}

redirect the whole if to a log file

if $metric > $threshold {
    print "system state is critical"
    print "metric = $metric"
} else {
    print "system is okay"
} >> debug.log

in for, pass only items that match a condition:
```
>> put 1 2 3 4 | for $i if $i <= 2
1
2
```
Check for documentation for the complete syntax.