Allow disabling logging by setting AUSTIN_NO_LOGGING in the environment

ChangeLog

@@ -2,6 +2,9 @@
 
  Added support for Python 3.11.
 
+ Allowed disabling logging by setting the environment variable
+ AUSTIN_NO_LOGGING.
+
  Improved permission error reporting on MacOS.
 
  Improved MacOS support.

README.md

@@ -355,6 +355,15 @@ where the structure of `[frame]` and the number and type of metrics on each line
 depend on the mode.
 
 
+## Environment variables
+
+Some behaviour of Austin can be configured via environment variables.
+
+| Variable | Effect |
+| ------------------- | ------ |
+| `AUSTIN_NO_LOGGING` | Disables all [log messages](#logging) (since Austin 3.4.0). |
+
+
 ## Normal Mode
 
 In normal mode, the `[frame]` part of each emitted sample has the structure
@@ -522,6 +531,8 @@ statistics. _Bad_ frames are output together with the other frames. In general,
 entries for bad frames will not be visible in a flame graph as all tests show
 error rates below 1% on average.
 
+Logging can be disabled using [environment variables](#environment-variables).
+
 
 ## Cheat sheet
 

src/logging.c

@@ -50,9 +50,11 @@ FILE * logfile = NULL;
 #include "austin.h"
 #include "logging.h"
 
+int logging = 1;
 
 void
 _log_writer(int prio, const char * fmt, va_list ap) {
+ if (!logging) return;
  #ifdef PL_UNIX
  vsyslog(prio, fmt, ap);
 
@@ -69,9 +71,16 @@ _log_writer(int prio, const char * fmt, va_list ap) {
  #endif
 }
 
+static int
+has_nonempty_env(const char * s) {
+ const char * v = getenv(s);
+ return v != NULL && *v != '\0';
+}
 
 void
 logger_init(void) {
+ if (has_nonempty_env("AUSTIN_NO_LOGGING")) logging = 0;
+ if (!logging) return;
  #ifdef PL_UNIX
  setlogmask (LOG_UPTO (LOG_DEBUG));
  openlog ("austin", LOG_CONS | LOG_PID | LOG_NDELAY, LOG_LOCAL1);
@@ -162,6 +171,7 @@ log_t(const char * fmt, ...) {
 
 void
 logger_close(void) {
+ if (!logging) return;
  #ifdef PL_UNIX
  closelog();
 

test/test_fork.py

@@ -235,3 +235,13 @@ def test_qualnames(py, austin):
 
  assert has_pattern(result.stdout, "qualnames.py:Foo.run"), compress(result.stdout)
  assert has_pattern(result.stdout, "qualnames.py:Bar.run"), compress(result.stdout)
+
+
+@allpythons()
+def test_no_logging(py, monkeypatch):
+ monkeypatch.setenv("AUSTIN_NO_LOGGING", "1")
+ result = austin("-i", "1ms", *python(py), target("target34.py"))
+ assert has_pattern(result.stdout, "target34.py:keep_cpu_busy:3"), compress(
+ result.stdout
+ )
+ assert result.returncode == 0, result.stderr or result.stdout