Should I return EXIT SUCCESS or 0 from main

Question

It s a simple question  but I keep seeing conflicting answers  should the main routine of a C   program return 0 or EXIT SUCCESS    include  lt cstdlib gt  int main   return EXIT SUCCESS     or  int main   return 0     Are they the exact same thing  Should EXIT SUCCESS only be used with exit       I thought EXIT SUCCESS would be a better option because other software may want to deem zero as failure  but I also heard that if you return 0  the compiler is capable of changing it to a different value anyway

User · Answer

0 is  by definition  a magic number  EXIT SUCCESS is almost universally equal to 0  happily enough   So why not just return exit 0     exit EXIT SUCCESS   is abundantly clear in meaning     exit 0    on the other hand  is counterintuitive in some ways   Someone not familiar with shell behavior might assume that 0    false    bad  just like every other usage of 0 in C   But no - in this one special case  0    success    good  For most experienced devs  not going to be a problem   But why trip up the new guy for absolutely no reason   tl dr - if there s a defined constant for your magic number  there s almost never a reason not to used the constant in the first place  It s more searchable  often clearer  etc  and it doesn t cost you anything

User · Answer

What you return from a program is just a convention   No  I can t think of any circumstances where  EXIT SUCCESS  wouldn t be  0    Personally  I d recommend  0    IMHO

User · Answer

This is a never ending story that reflect the limits  an myth  of  interoperability and portability over all    What the program should return to indicate  success  should be defined by who is receiving the value  the Operating system  or the process that invoked the program  not by a language specification    But programmers likes to write code in  portable way  and hence they invent their own model for the concept of  operating system  defining symbolic values to return   Now  in a many-to-many scenario  where many languages serve to write programs to many system  the correspondence between the language convention for  success  and the operating system one  that no one can grant to be always the same  should be handled by the specific implementation of a library for a specific target platform   But - unfortunatly - these concept where not that clear at the time the C language was deployed  mainly to write the UNIX kernel   and Gigagrams of books where written by saying  return 0 means success   since that was true on the OS at that time having a C compiler   From then on  no clear standardization was ever made on how such a correspondence should be handled  C and C   has their own definition of  return values  but no-one grant a proper OS translation  or better  no compiler documentation say anything about it   0 means success if true for UNIX - LINUX and -for independent reasons- for Windows as well  and this cover 90  of the existing  consumer computers   that - in the most of the cases - disregard the return value  so we can discuss for decades  bu no-one will ever notice    Inside this scenario  before taking a decision  ask these questions   - Am I interested to communicate something to my caller about my existing   If I just always return 0     there is no clue behind the all thing   - Is my caller having conventions about this communication    Note that a single value is not  a convention  that doesn t allow any information representation   If both of this answer are no  probably the good solution is don t write the main return statement at all   And let the compiler to decide  in respect to the target is working to    If no convention are in place 0 success meet the most of the situations  and using symbols may be problematic  if they introduce a convention    If conventions are in place  ensure to use symbolic constants that are coherent with them  and ensure convention coherence  not value coherence  between platforms

User · Answer

EXIT FAILURE  either in a return statement in main or as an argument to exit    is the only portable way to indicate failure in a C or C   program   exit 1  can actually signal successful termination on VMS  for example   If you re going to be using EXIT FAILURE when your program fails  then you might as well use EXIT SUCCESS when it succeeds  just for the sake of symmetry   On the other hand  if the program never signals failure  you can use either 0 or EXIT SUCCESS   Both are guaranteed by the standard to signal successful completion    It s barely possible that EXIT SUCCESS could have a value other than 0  but it s equal to 0 on every implementation I ve ever heard of    Using 0 has the minor advantage that you don t need  include  lt stdlib h gt  in C  or  include  lt cstdlib gt  in C    if you re using a return statement rather than calling exit    -- but for a program of any significant size you re going to be including stdlib directly or indirectly anyway   For that matter  in C starting with the 1999 standard  and in all versions of C    reaching the end of main   does an implicit return 0  anyway  so you might not need to use either 0 or EXIT SUCCESS explicitly    But at least in C  I consider an explicit return 0  to be better style     Somebody asked about OpenVMS  I haven t used it in a long time  but as I recall odd status values generally denote success while even values denote failure   The C implementation maps 0 to 1  so that return 0  indicates successful termination  Other values are passed unchanged  so return 1  also indicates successful termination  EXIT FAILURE would have a non-zero even value

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Once you start writing code that can return a myriad of exit statuses  you start  define ing all of them  In this case EXIT SUCCESS makes sense in context of not being a  magic number   This makes your code more readable because every other exit code will be EXIT SOMETHING  If you simply write a program that will return when it s done  return 0 is valid  and probably even cleaner because it suggests that there s no sophisticated return code structure

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If you use EXIT SUCCESS  your code will be more portable   http   www dreamincode net forums topic 57495-return-0-vs-return-exit-success

User · Answer

Some compilers might create issues with this - on a Mac C   compiler  EXIT SUCCESS worked fine for me but on a Linux C   complier I had to add cstdlib for it to know what EXIT SUCCESS is  Other than that  they are one and the same

User · Answer

It does not matter  Both are the same   C   Standard Quotes          If the value of status is zero or EXIT SUCCESS  an implementation-defined form of the status successful termination is returned

[c++] Should I return EXIT_SUCCESS or 0 from main()?

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