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ERROR.C
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─────Run-Time Library───────────────────────────────────────────────────────
/* ERROR.C illustrates stream file error handling. Functions illustrated
* include:
* ferror clearerr exit _exit
* perror strerror _strerror
*
* The _exit routine is not specifically illustrated, but it is the same
* as exit except that file buffers are not flushed and atexit and _onexit
* are not called.
*/
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <errno.h>
enum BOOL { FALSE, TRUE };
void errortest( FILE *stream, char *msg, int fterm ); /* Prototype */
FILE *stream;
char string[] = "This should never be written";
void main( int argc, char *argv[] )
{
/* Open file and test to see if open caused error. If so, terminate. */
stream = fopen( argv[1], "r" );
errortest( stream, "Can't open file", TRUE );
/* Try to write to a read-only file, then test to see if write
* caused error. If so, clear error, but don't terminate.
*/
fprintf( stream, "%s\n", string );
errortest( stream, "Can't write file", FALSE );
exit( 0 );
}
/* Tests a stream to see if there is an error on it. If so, prints the
* msg argument and terminates if the fterm flag is set.
*/
void errortest( FILE *stream, char *msg, int fterm )
{
/* If stream doesn't exist (failed fopen) or if there is an error
* on the stream, handle error.
*/
if( (stream == NULL) || (ferror( stream )) )
{
perror( msg );
/* _strerror and strerror can be used to get the same result
* as perror, as illustrated by these lines (commented out).
printf( "%s: %s\n", msg, strerror( errno ) );
printf( _strerror( msg ) );
*/
/* Terminate or clear error, depending on terminate flag. */
if( fterm )
exit( errno );
else
clearerr( stream );
}
}
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