ESP32 Forum

Hello.

ESP IDF , Master (or 4.4) , ESP32 (ESP32-PICO-D4) .

Periodicaly (i'm do not know cause) 'printf' is no output to defaut uart, if non-constant format, i.e :

---
printf ("test\n"); // output: test
printf ("number %d\n", 1); // no output
char * line = "line\n";
printf (line); // no output
---

but,
---
fprintf (stdout, "number %d\n", 1); // output: number 1
---

'printf(CONSTANT)' is have output, maybe, because gcc replace 'printf(CONSTANT)' to 'puts(CONSTANT)'.

=================

I'm build tcp server in project, and connect to it from terminal on PC.
All ommited 'printf' output i see in terminal.

How to prevent redirect 'printf' output?

Is it possible that you are overriding 'stdout' stream anywhere in your code? This would explain why printf output (which uses stdout) goes to the TCP connection and 'stderr' is still printed to the console.

If you can find the minimal code to reproduce this issue, please report it at https://github.com/espressif/esp-idf/issues and we will take a look.

Thanks.

I temporary removed all my modules, excluding main.c from build in my project.
Printf have output in app_main(). Now i will add module by module to localize problem.

My modules are not change explicitly vfs , stdout, etc... but are used many SDK components.

Many stdio libraries will buffer a printf() / stdout stream, collecting characters and sending them as a group, usually triggered by a line feed.
Try disabling stdout buffering:

setvbuf(stdout, NULL, _IONBF, 0); // Disable stdout buffering