i recently found out that it should be only int main() and not void main() as per standards.
also,i found out that the return value is 0 in case of a normal termination.
but what is the use of this return value?where can it be used?
now don't gun me down as usualim just a beginner.
The shell calling the program receives the return value. In Windows console, for example, this value is retrieved through the ERRORLEVEL environment variable. In the BASH shell, it's the $? environment variable.
In typical bash scripts the variable $? (as mentioned above) is checked after important commands.
The script continues if it is 0 (or depending upon the program, something else) and handles the errors if it denotes an error.
I'm pretty sure the C standard does not specify which value (e.g. 0) is for success. I think that's up to the OS/environment, but *nix systems generally use 0 for success. The standard does however define two macros, EXIT_FAILURE and EXIT_SUCCESS that are safe and portable, and probably your best bet. Another thing to note, main is always specified as returning int, but the OS/environment may interpret that as signed or unsigned, and as a char, short or int. E.g.
Linux interprets the return code as a signed char. Not sure what windows does.Code:$ cat foo.c int main(void) { return -1; } $ gcc -Wall foo.c -o foo $ ./foo $ echo $? 255
0 is always success as well.
Even on those systems (such as VMS) where "success" is a non-zero value.
However, if you return something else (other than 0 or the two constants), then you will need to check how your environment interprets specific return values.
If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
If at first you don't succeed, try writing your phone number on the exam paper.
Actually the minimum C program is..Originally Posted by theju112
i recently found out that it should be only int main() and not void main() as per standards.
also,i found out that the return value is 0 in case of a normal termination.
but what is the use of this return value?where can it be used?
now don't gun me down as usual
The returned value in windows can be used by batch files (IF ERRORLEVEL) or by other programs (In the case of CreateProcess()) to judge the sucess or failure of a program. A program that returns a non-0 value might well be considered to have failed.Code:int main (void) { // your code here return ErrorCode; } // typically this is 0
Now for the "shooting you down part"... In your first thread, you were told this at least half a dozen times and roundly ignored it.
unsigned int ... so that programs can report windows error codes when returning.
this is the exact answer i needed.
any other value apart from 0 would indicate an error. so the return value is used for error handling.
Last edited by theju112; 08-19-2011 at 05:47 PM.
If you return any value other than 0 or EXIT_SUCCESS, that would indicate an error. Note: The actual value returned to the OS is implementation defined.
Last edited by AndrewHunter; 08-19-2011 at 05:56 PM.
Warning: Some or all of my posted code may be non-standard and as such should not be used and in no case looked at.
Also note that many return values may not constitue errors... One example is in batch files, where the ERRORLEVEL keyword contains the return value from the process... You might use 0 to continue along, 10 to branch to a different place in the script, 123 might take you some where else...
A great many programs return values that are not, strictly speaking, errors.
Another example is a child program hatched with CreateProcess()... it's return value can be used to signal it's parent what to do next using GetExitCodeProcess() in a switch statement... In that case you can have hundreds of possiblities...
The only true error returned to the OS is EXIT_FAILURE.
