The Single UNIX ® Specification, Version 2
Copyright © 1997 The Open Group


fgetc - get a byte from a stream


#include <stdio.h>

int fgetc(FILE *stream);


The fgetc() function obtains the next byte (if present) as an unsigned char converted to an int, from the input stream pointed to by stream, and advances the associated file position indicator for the stream (if defined).

The fgetc() function may mark the st_atime field of the file associated with stream for update. The st_atime field will be marked for update by the first successful execution of fgetc(), fgets(), fgetwc(), fgetws(), fread(), fscanf(), getc(), getchar(), gets() or scanf() using stream that returns data not supplied by a prior call to ungetc() or ungetwc().


Upon successful completion, fgetc() returns the next byte from the input stream pointed to by stream. If the stream is at end-of-file, the end-of-file indicator for the stream is set and fgetc() returns EOF. If a read error occurs, the error indicator for the stream is set, fgetc() returns EOF and sets errno to indicate the error.


The fgetc() function will fail if data needs to be read and:
The O_NONBLOCK flag is set for the file descriptor underlying stream and the process would be delayed in the fgetc() operation.
The file descriptor underlying stream is not a valid file descriptor open for reading.
The read operation was terminated due to the receipt of a signal, and no data was transferred.
A physical I/O error has occurred, or the process is in a background process group attempting to read from its controlling terminal, and either the process is ignoring or blocking the SIGTTIN signal or the process group is orphaned. This error may also be generated for implementation-dependent reasons.
The file is a regular file and an attempt was made to read at or beyond the offset maximum associated with the corresponding stream.

The fgetc() function may fail if:

Insufficient storage space is available.
A request was made of a non-existent device, or the request was outside the capabilities of the device.




If the integer value returned by fgetc() is stored into a variable of type char and then compared against the integer constant EOF, the comparison may never succeed, because sign-extension of a variable of type char on widening to integer is implementation-dependent.

The ferror() or feof() functions must be used to distinguish between an error condition and an end-of-file condition.




feof(), ferror(), fopen(), getchar(), getc(), <stdio.h>.


Derived from Issue 1 of the SVID.

UNIX ® is a registered Trademark of The Open Group.
Copyright © 1997 The Open Group
[ Main Index | XSH | XCU | XBD | XCURSES | XNS ]