Programming in C

474 Appendix B The Standard C Library
Included in this file are declarations for the I/O functions and definitions for the names
EOF, NULL, stdin, stdout, stderr (all constant values), and FILE.
In the descriptions that follow, fileName, fileName1, fileName2, accessMode, and
format are pointers to null-terminated strings, buffer is a pointer to a character array,
filePtr is of type “pointer to FILE,” n and size are positive integer values of type
size_t,and i and c are of type int.
void clearerr (filePtr)
Clears the end of file and error indicators associated with the file identified by
filePtr.
int fclose (filePtr)
Closes the file identified by filePtr and returns zero if the close is successful, or
returns EOF if an error occurs.
int feof (filePtr)
Returns nonzero if the identified file has reached the end of the file and returns zero
otherwise.
int ferror (filePtr)
Checks for an error condition on the indicated file and returns zero if an error exists,
and returns nonzero otherwise.
int fflush (filePtr)
Flushes (writes) any data from internal buffers to the indicated file, returning zero on
success and the value EOF if an error occurs.
int fgetc (filePtr)
Returns the next character from the file identified by filePtr, or the value EOF if an
end-of-file condition occurs. (Remember that this function returns an int.)
int fgetpos (filePtr, fpos)
Gets the current file position for the file associated with filePtr, storing it into the
fpos_t (defined in ) variable pointed to by fpos. fgetpos returns zero on
success, and returns nonzero on failure. See also the fsetpos function.
char *fgets (buffer, i, filePtr)
Reads characters from the indicated file, until either i – 1 characters are read or a
newline character is read, whichever occurs first. Characters that are read are stored
into the character array pointed to by buffer. If a newline character is read, it will be
stored in the array. If an end of file is reached or an error occurs, the value NULL is
returned; otherwise, buffer is returned.