Sun Microsystems, Inc.
spacerspacer
spacer   www.sun.com docs.sun.com | | |  
spacer
black dot
   
A   B   C   D   E   F   G   H   I   J   K   L   M   N   O   P   Q   R   S   T   U   V   W   X   Y   Z
    
 
Standard C Library Functionsfgetc(3C)


NAME

 fgetc, getc, getc_unlocked, getchar, getchar_unlocked, getw - get a byte from a stream

SYNOPSIS

 
#include <stdio.h>
int fgetc(FILE *stream);
 int getc(FILE *stream);
 int getc_unlocked(FILE *stream);
 int getchar(void);
 int getchar_unlocked(void);
 int getw(FILE *stream);

DESCRIPTION

 

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(3C), fgetwc(3C), fgetws(3C), fread(3C), fscanf(3C), getc(), getchar(), gets(3C) or scanf(3C) using stream that returns data not supplied by a prior call to ungetc(3C) or ungetwc(3C).

The getc() routine is functionally identical to fgetc(), except that it is implemented as a macro. It runs faster than fgetc(), but it takes up more space per invocation and its name cannot be passed as an argument to a function call.

The getchar() routine is equivalent to getc(stdin). It is implemented as a macro.

The getc_unlocked() and getchar_unlocked() routines are variants of getc() and getchar(), respectively, that do not lock the stream. It is the caller's responsibility to acquire the stream lock before calling these routines and releasing the lock afterwards; see flockfile(3C) and stdio(3C). These routines are implemented as macros.

The getw() function reads the next word from the stream. The size of a word is the size of an int and may vary from environment to environment. The getw() function presumes no special alignment in the file.

The getw() 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(3C), fread(3C), getc(), getchar(), gets(3C), fscanf(3C) or scanf(3C) using stream that returns data not supplied by a prior call to ungetc(3C).

RETURN VALUES

 

Upon successful completion, fgetc(), getc(), getc_unlocked(), getchar(), getchar_unlocked(), and getw() return 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 these functions return EOF. If a read error occurs, the error indicator for the stream is set, EOF is returned, and errno is set to indicate the error.

ERRORS

 

The fgetc(), getc(), getc_unlocked(), getchar(), getchar_unlocked(), and getw() functions will fail if data needs to be read and:

EAGAIN
The O_NONBLOCK flag is set for the file descriptor underlying stream and the process would be delayed in the fgetc() operation.
EBADF
The file descriptor underlying stream is not a valid file descriptor open for reading.
EINTR
The read operation was terminated due to the receipt of a signal, and no data was transferred.
EIO
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.
EOVERFLOW
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(), getc(), getc_unlocked(), getchar(), getchar_unlocked(), and getw() functions may fail if:

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

USAGE

 

If the integer value returned by fgetc(), getc(), getc_unlocked(), getchar(), getchar_unlocked(), and getw() 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(3C) or feof(3C) functions must be used to distinguish between an error condition and an end-of-file condition.

Functions exist for the getc(), getc_unlocked(), getchar(), and getchar_unlocked() macros. To get the function form, the macro name must be undefined (for example, #undef getc).

When the macro forms are used, getc() and getc_unlocked() evaluate the stream argument more than once. In particular, getc(*f++); does not work sensibly. The fgetc() function should be used instead when evaluating the stream argument has side effects.

Because of possible differences in word length and byte ordering, files written using getw() are machine-dependent, and may not be read using getw() on a different processor.

The getw() function is inherently byte stream-oriented and is not tenable in the context of either multibyte character streams or wide-character streams. Application programmers are recommended to use one of the character-based input functions instead.

ATTRIBUTES

 

See attributes(5) for descriptions of the following attributes:

ATTRIBUTE TYPEATTRIBUTE VALUE
MT-LevelSee NOTES below.

SEE ALSO

 

intro(3), fclose(3C), feof(3C), fgets(3C), fgetwc(3C), fgetws(3C), flockfile(3C), fopen(3C), fread(3C), fscanf(3C), gets(3C), putc(3C), scanf(3C), stdio(3C), ungetc(3C), ungetwc(3C), attributes(5)

NOTES

 

The fgetc(), getc(), getchar(), and getw() routines are MT-Safe in multithreaded applications. The getc_unlocked() and getchar_unlocked() routines are unsafe in multithreaded applications.


SunOS 5.9Go To TopLast Changed 3 Feb 1998

 
      
      
Copyright 2002 Sun Microsystems, Inc. All rights reserved. Use is subject to license terms.