How to fix C error 'stderr undeclared'

Problem:

You have C code like

main.c

fprintf(stderr, "test");

fprintf(stderr, "test");

but when you try to compile it you see an error message like

error_message.txt

/home/uli/myproject/main.c:9:25: error: ‘stderr’ undeclared (first use in this function)
                 fprintf(stderr, "test");

/home/uli/myproject/main.c:9:25: error: ‘stderr’ undeclared (first use in this function)
                 fprintf(stderr, "test");

Solution

Add

stdio_include.c

#include <stdio.h>

#include <stdio.h>

at the top of the source file where the error occured. Including stdio.h will include symbols like printf, fprintf, stdin, stdout and stderr.

Check out similar posts by category: Allgemein

If this post helped you, please consider buying me a coffee or donating via PayPal to support research & publishing of new posts on TechOverflow

Buy me a coffee