Content-type: text/html Man page of getc

getc

Section: C Library Functions (3)
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NAME

getc, fgetc, getc_unlocked, getchar, getchar_unlocked, getw - Get a byte or word from an input stream  

LIBRARY

Standard C Library (libc.so, libc.a)  

SYNOPSIS

#include <stdio.h>

int getc(
        FILE *stream);

int fgetc(
        FILE *stream);

int getc_unlocked(
        FILE * stream);

int getchar(void);

int getchar_unlocked(void);

int getw(
        FILE *stream);  

STANDARDS

Interfaces documented on this reference page conform to industry standards as follows:

getc_unlocked, getchar_unlocked:  POSIX.1c

fgetc(), getc(), getchar(), getw():  XPG4, XPG4-UNIX

Refer to the standards(5) reference page for more information about industry standards and associated tags.  

PARAMETERS

Points to the file structure of an open file.  

DESCRIPTION

The getc() function returns the next byte from the input specified by the stream parameter and moves the file pointer, if defined, ahead one byte in stream. The getc() function may be a macro (depending on compile-time definitions). See the NOTES section for more information.

The fgetc() function performs the same function as getc().

The getchar() function returns the next byte from stdin, the standard input stream. Note that getchar() can also be a macro.

[Digital]  The reentrant versions of these functions are all locked against multiple threads calling them simultaneously. This will incur an overhead to ensure integrity of the stream. The unlocked versions of these calls, getc_unlocked() and getchar_unlocked() may be used to avoid the overhead. The getc_unlocked() and getchar_unlocked() functions are functionally identical to the getc() and getchar() functions, except that getc_unlocked() and getchar_unlocked() may be safely used only within a scope that is protected by the flockfile() and funlockfile() functions used as a pair. The caller must ensure that the stream is locked before these functions are used. The getc() and getchar() functions can also be macros.

The getw() function reads the next word (int) from the stream. The size of a word is the size of an int, which may vary from one machine architecture to another. The getw() function returns the constant EOF at the end of the file or when an error occurs. Since EOF is a valid integer value, the feof() and ferror() functions can be used to check the success of getw(). The getw() function assumes no special alignment in the file.

Because of possible differences in int length and byte ordering from one machine architecture to another, files written using the putw() subroutine are machine dependent and may not be readable using getw() on a different type of processor.  

NOTES

The getc() and getchar() functions may be macros (depending on the compile-time definitions used in the source). Consequently, you cannot use these interfaces where a function is necessary; for example, a subroutine pointer cannot point to one of these interfaces. In addition, getc() does not work correctly with a stream parameter that has side effects. In particular, the following does not work:


        getc(*f++) In cases like this one, use the fgetc() function instead.  

RETURN VALUES

Upon successful completion, these functions and macros return the next byte or word from the input stream. If the stream is at end-of-file, the end-of-file indicator for the stream is set and the integer constant EOF is returned. 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 set errno to the specified value for the following conditions: The O_NONBLOCK flag is set for the underlying stream and the process would be delayed by the read operation. The file descriptor underlying the stream is not a valid file descriptor or is not open for reading. The read operation was interrupted by a signal which was caught and no data was transferred. The call is attempting to read from the process's controlling terminal and either the process is ignoring or blocking the SIGTTIN signal or the process group is orphaned.

[XPG4-UNIX]  A physical I/O error has occurred. Insufficient memory is available for the operation. The device associated with stream does not exist.
 

RELATED INFORMATION

Functions: flockfile(3), funlockfile(3), gets(3), getwc(3), putc(3)

Standards: standards(5) delim off


 

Index

NAME
LIBRARY
SYNOPSIS
STANDARDS
PARAMETERS
DESCRIPTION
NOTES
RETURN VALUES
ERRORS
RELATED INFORMATION

This document was created by man2html, using the manual pages.
Time: 02:42:09 GMT, October 02, 2010