EXCEPTION::LOGERR 1g 2025-09-11 laplante@plcb.ca GOWEB/EXCEPTION

title: “EXCEPTION::LOGERR” author: “laplante@plcb.ca” date: “2025-09-11” version: “1.0.1”

caregory: “GOWEB/EXCEPTION”

Name

exception::logerr — print a formatted message to stderr (CLI) or error logfile (Web)

Synopsis

exception::logErr(format[, args])
logErr(format[, args])
exception::logerr(format[, args])
logerr(format[, args])

Description

This function is the equivalent of Golang printf.

In CLI, it prints to stderr.
In Web, it writes to the error logfile.

The format string supports the following verbs:

General

%!v(MISSING) : default format. For structs, %!v(MISSING) adds field names.
%!v(MISSING) : Go-syntax representation of the value.
%!T(MISSING) : type of the value.
% : literal percent sign.

Boolean

%!t(MISSING) : prints true or false.

Integer

%!b(MISSING) : base 2.
%!c(MISSING) : character represented by Unicode code point.
%!d(MISSING) : base 10.
%!o(MISSING) : base 8.
%!O(MISSING) : base 8 with 0o prefix.
%!q(MISSING) : single-quoted character literal, safely escaped with Go syntax.
%!x(MISSING) : base 16, lower-case.
%!X(MISSING) : base 16, upper-case.
%!U(MISSING) : Unicode format, e.g. U+1234.

Floating-point and complex

%!b(MISSING) : decimalless scientific notation, exponent a power of two.
%!e(MISSING) / %!E(MISSING) : scientific notation.
%!f(MISSING) / %!F(MISSING) : decimal point, no exponent.
%!g(MISSING) / %!G(MISSING) : compact format depending on exponent size.
%!x(MISSING) / %!X(MISSING) : hexadecimal floating-point.

String

%!s(MISSING) : uninterpreted bytes of string.
%!q(MISSING) : double-quoted, safely escaped.
%!x(MISSING) : base 16, two characters per byte, lowercase.
%!X(MISSING) : base 16, two characters per byte, uppercase.

Pointer

%!p(MISSING) : base 16 notation with 0x prefix.
%!b(MISSING), %!d(MISSING), %!o(MISSING), %!x(MISSING), %!X(MISSING) also work with pointers.

Defaults

bool → %!t(MISSING)
int, int8… → %!d(MISSING)
uint, uint8… → %!d(MISSING), %!x(MISSING) if %!v(MISSING) used
float32… → %!g(MISSING)
string → %!s(MISSING)

Width & Precision

%!f(MISSING) → default width, precision.
%!f(MISSING) → width 9, default precision.
%!f(MISSING) → precision 2.
%!f(MISSING) → width 9, precision 2.
%!f(MISSING) → width 9, precision 0.

Flags

+ : always print sign.
- : left-justify.
# : alternate format (e.g. 0b, 0o, 0x).
: leave space for elided sign.
0 : pad with zeros.

Examples

res={{
    a := [1, 2.2, "3"];
    logerr("%!T(MISSING) %!T(MISSING) %!T(MISSING)\n", a);
}}.

Return:

res=int64 float64 string

res={{
    a := [1, 2.2, "3", [1,2,3]];
    logerr("%!T(MISSING) %!T(MISSING) %!T(MISSING) %!T(MISSING)\n", a);
}}.