Difference between return 1 return 0 return -1 and exit

Question

For example consider following code   int main int argc char  argv         int  p  q     p    int   malloc sizeof int  10      q    int   malloc sizeof int  10      if  p    0        printf  ERROR  Out of memory n            return 1         if  q    0        printf  ERROR  Out of memory n            exit 0         return 0      What does return 0  return 1  exit 0  do in the above program  exit 0  will exit total program and control comes out of loop but what happens in case of return 0  return 1  return -1

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return from main   is equivalent to exit  the program terminates immediately execution with exit status set as the value passed to return or exit  return in an inner function  not main  will terminate immediately the execution of the specific function returning the given result to the calling function   exit from anywhere on your code will terminate program execution immediately     status 0 means the program succeeded   status different from 0 means the program exited due to error or anomaly   If you exit with a status different from 0 you re supposed to print an error message to stderr so instead of using printf better something like  if errorOccurred        fprintf stderr   meaningful message here n        return -1      note that  depending on the OS you re on  there are some conventions about return codes   Google for  exit status codes  or similar and you ll find plenty of information on SO and elsewhere     Worth mentioning that the OS itself may terminate your program with specific exit status codes if you attempt to do some invalid operations like reading memory you have no access to

User · Answer

return n from main is equivalent to exit n    The valid returned is the rest of your program  It s meaning is OS dependent  On unix  0 means normal termination and non-zero indicates that so form of error forced your program to terminate without fulfilling its intended purpose   It s unusual that your example returns 0  normal termination  when it seems to have run out of memory

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return n from your main entry function will terminate your process and report to the parent process  the one that executed your process  the result of your process  0 means SUCCESS  Other codes usually indicates a failure and its meaning

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To indicate execution status   status 0 means the program succeeded   status different from 0 means the program exited due to error or anomaly   return n  from your main entry function will terminate your process and report to the parent process  the one that executed your process  the result of your process  0 means SUCCESS  Other codes usually indicates a failure and its meaning

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As explained here  in the context of main both return and exit do the same thing  Q  Why do we need to return or exit    A  To indicate execution status   In your example even if you didnt have return or exit statements the code would run fine  Assuming everything else is syntactically etc-ally correct  Also  if  and it should be  main returns int you need that return 0 at the end    But  after execution you don t have a way to find out if your code worked as expected  You can use the return code of the program  In  nix environments   using     which gives you the code  as set by exit or return    Since you set these codes yourself you understand at which point the code reached before terminating   You can write return 123 where 123 indicates success in the post execution checks   Usually  in  nix environments 0 is taken as success and non-zero codes as failures

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return in function return execution back to caller and exit from function terminates the program   in main function return 0 or exit 0  are same but if you write exit 0  in different function then you program will exit from that position   returning different values like return 1 or return -1 means that program is returning error    When exit 0  is used to exit from program  destructors for locally scoped non-static objects are not called  But destructors are called if return 0 is used

[c] Difference between return 1, return 0, return -1 and exit?

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