Standard C Library Functions fgetc(3C)
NAME
fgetc, getc, getc_unlocked, getchar, getchar_unlocked, getw
- get a byte from a stream
SYNOPSIS
#include
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 streampointed to by stream, and advances the associated file posi-
tion indicator for the stream (if defined).For standard-conforming (see standards(5)) applications, if
the end-of-file indicator for the stream is set, fgetc()
returns EOF whether or not a next byte is present.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), fread(3C), fscanf(3C), getc(), getchar(), getdelim(3C), getline(3C), gets(3C) or scanf(3C) using stream that returns data not supplied by a prior call to ungetc(3C) or ungetwc(3C). The getc() function 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.SunOS 5.11 Last change: 15 Oct 2003 1
Standard C Library Functions fgetc(3C) 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 bystream. If the stream is at end-of-file, the end-of-file
indicator for the stream is set and these functions returnEOF. For standard-conforming (see standards(5)) applica-
tions, if the end-of-file indicator for the stream is set,
these functions return EOF whether or not the stream is atend-of-file. 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.SunOS 5.11 Last change: 15 Oct 2003 2
Standard C Library Functions fgetc(3C) 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 pro-
cess is in a background process group attempt-
ing 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 forimplementation-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 neversucceed, 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 distin-
guish between an error condition and an end-of-file condi-
tion.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,SunOS 5.11 Last change: 15 Oct 2003 3
Standard C Library Functions fgetc(3C) 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 ord-
ering, 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 characterstreams 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 attri-
butes:____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
| ____________________________|_____________________________|_
| Interface Stability | fgetc(), getc(),|| | getc_unlocked(), getchar(),|
| | and getchar_unlocked() are|
| | Standard. ||_____________________________|_____________________________|
| MT-Level | See NOTES below. |
|_____________________________|_____________________________|
SEE ALSO
Intro(3), __fsetlocking(3C), fclose(3C), feof(3C),
fgets(3C), fgetwc(3C), fgetws(3C), flockfile(3C), fopen(3C), fread(3C), fscanf(3C), getdelim(3C), getline(3C), gets(3C), putc(3C), scanf(3C), stdio(3C), ungetc(3C), ungetwc(3C), attributes(5), standards(5) NOTESThe 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 5.11 Last change: 15 Oct 2003 4