Man Pages – Linux Manual Pages

errno – number of last error
USAGE
#include <errno.h>

DESCRIPTION
The header file defines the integer variable errno, which is
set by system calls and some library functions in the event of an error
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assert_perror – test errnum and abort
USAGE
#define _GNU_SOURCE
#include <assert.h>

void assert_perror(int errnum);

DESCRIPTION
If the macro NDEBUG was defined at the moment was last
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