Macros to the rescue

Try using macros in C:

  #include <assert.h>
  #define Chksys0(s) assert( (s) == 0 )
  #define Chksys1(s) assert( (s) >= 0 )

And write
  
  Chksys0( unlink("filename") );
  Chksys0( bytes = read( fd, buffer, 100 ) );
  Chksys1( fd = open( FILENAME, O_RDWR|O_EXCL|O_CREAT, 0666 ) );
  Chksys1( time( &t ) );

In Perl, return value is usually true/false in a logical way.

(Macro idea based on excerpt from "Practical Unix & Internet Security, 3rd Edition", Garfinkel/Spafford/Schwartz. Go buy this book.)