C in a Nutshell

Name

exit

Synopsis

Terminates the program normally

#include <stdlib.h>
voidexit( int status );

The exit() function ends the program and returns a value to the operating environment to indicate the program’s final status. Control never returns from the exit() function.

Before terminating the program, exit() calls any functions that have been registered by the atexit() function (in LIFO order), closes any open files, and deletes any files created by the tmpfile() function.

The file stdlib.h defines two macros for use as arguments to exit(): EXIT_SUCCESS and EXIT_FAILURE. If the argument is equal to one of these values, the program returns a corresponding system-specific value to the operating system to indicate success or failure. An argument value of 0 is treated the same as EXIT_SUCCESS. For other argument values, the value returned to the host environment is determined by the implementation.

Example

FILE *f_in, *f_out;

enum { X_OK = 0, X_ARGS, X_NOIN, X_NOOUT };

if ( argc != 3 ) {
  fprintf( stderr, "Usage: program input-file output-file\n");exit( X_ARGS );
}

f_in  = fopen(argv[1], "r");
if ( f_in == NULL ) {
  fprintf( stderr, "Unable to open input file.\n");
  exit( X_NOIN );
}
f_out = fopen(argv[2], "a+");
if ( f_out == NULL ) {
  fprintf( stderr, "Unable to open output file.\n");
  exit( X_NOOUT );
}

/* ... read, process, write, close files ... */

exit( X_OK );

See Also

_Exit(), atexit(), abort()