HP 3000 Manuals HP 3000 Manuals
feof
Tests whether the end-of-file indicator for a stream has been set.
Syntax
#include <stdio.h>
int feof (FILE *stream);
Parameters
stream A pointer to a file to be tested.
Return Values
=0 End-of-file has not been set.
!=0 End-of-file has been set.
Description
The feof function is intended to clarify ambiguous return values from
standard I/O functions.
The feof function returns a nonzero value if the end-of-file indicator
was set on the specified stream. It does not reset the indicator. You
need to use the clearerr function to reset it.
Because I/O functions return EOF for end-of-file and error conditions,
you can use feof() and ferror() to distinguish between them. Also, some
systems support I/O functions that take integer data instead of
characters. For these functions, you need to use feof() and ferror() to
differentiate between valid data and the EOF flag.
Example
The following program uses feof():
#include <stdio.h>
main(argc, argv)
int argc;
char *argv[ ];
{
int c;
FILE *dfile, *datale, *datagt;
if(argc != 2) {
fprintf(stderr, "usage: intsort filename\n");
exit(1);
}
dfile = fopen(argv[1], "r");
if(dfile == NULL) {
fprintf("Can't open %s.\n", argv[1]);
exit(1);
}
datale = fopen("dfle", "w");
if(datale == NULL) {
fprintf("Can't create dfle file.\n");
exit(1);
}
datagt = fopen("dfgt", "w");
if(datagt == NULL) {
fprintf("Can't create dfgt file.\n");
exit(1);
}
for(;;) {
if((c = fgetc(dfile)) != EOF) {
if(c <= 'Z' && c >= 'A')
fputc(c, datale);
else
fputc(c, datagt);
} else {
if(feof(dfile))
break;
else
fprintf(stderr, "error in reading file \n");
exit(1);
}
}
exit(0);
}
Whenever fgetc() returns an integer equal to EOF, the feof() function
checks whether the end-of-file has been reached. If the end-of-file has
been reached, the loop and the program terminate; if not, an error
message is displayed and the program terminates.
See Also
fopen(), ferror(), ANSI C 4.9.10.2, POSIX.1 8.1