Output Format

Output Format

[timestamp] |PID| prefix [LEVEL] file:line (module) message

Field	Present	Example
timestamp	with set_timestamps(true): UTC, millisecond precision	[2026-09-30T08:15:02.417]
PID	always; a child of fork() shows its own	|4242|
prefix	always, set with set_prefix() (default ==ct==, up to 63 characters)	==ct==
LEVEL	always	[DEBUG], [INFO], [WARN], [ERROR]
file:line	with set_source_location(true), base name of the file	main.cpp:42
module	for tagged messages, when the name is not empty	(alloc)
message	the formatted message, as given	retrying 10.0.0.1

The library does not add a newline: end your format strings with \n.

Examples

coretrace::log(Level::Info, "plain\n");
coretrace::log(Level::Warn, Module("alloc"), "tagged\n");

|4242| ==ct== [INFO] plain
|4242| ==ct== [WARN] (alloc) tagged

With timestamps, source locations and a custom prefix:

[2026-09-30T08:15:02.417] |4242| ==myapp== [WARN] main.cpp:60 (db) Connection pool exhausted, count=0

Special cases

• An empty message (log(Level::Info, "")) writes nothing.
• An invalid format string writes coretrace: log format error followed by a newline instead of the line, with no prefix. The format string is only checked at run time, so log(Level::Info, "{} {}\n", 1) compiles.
• When colors are on, the PID, prefix, level, location and module are wrapped in ANSI sequences (see Configuration).