HP-UX Reference (11i v1 05/09) - 3 Library Functions A-M (vol 6)

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getc(3S) getc(3S)

ERRORS

getc(), getc_unlocked()

, getchar(), getchar_unlocked()

, getw(),

getw_unlocked()

, and fgetc() fail if data needs to be read into the stream’s buffer, and:

[EAGAIN] The O_NONBLOCK ﬂag is set for the ﬁle descriptor underlying stream and the process

would be delayed in the read 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 either no data

was transferred or the implementation does not report partial transfer for this ﬁle.

[EIO] A physical I/O error has occurred, or the process is a member of a background process

and is attempting to read from its controlling terminal, and either the process is

ignoring or blocking the SIGTTIN signal or the process group of the process is

orphaned.

Additional errno values may be set by the underlying

read() function (see read(2)).

WARNINGS

getc() and getchar() are implemented both as library functions and macros. The macro versions,

which are used by default, are deﬁned in <stdio.h>. To obtain the library function either use a

#undef

to remove the macro deﬁnition or, if compiling in ANSI-C mode, enclose the function name in parenthesis or

use the function address. The following example illustrates each of these methods :

#include <stdio.h>

#undef getc

...

main()

{

int (*get_char()) ();

...

return_val=getc(c,fd);

...

return_val=(getc)(c,fd1);

...

get_char = getchar;

};

If the integer value returned by getc(), getc_unlocked()

, getchar() ,

getchar_unlocked()

,orfgetc() is stored into a character variable then compared against the

integer constant

EOF, the comparison may never succeed because sign-extension of a character on widening

to integer is machine-dependent.

The macro version of getc() incorrectly treats a stream argument with side effects. In particular,

getc(*f++) does not work sensibly. The function version of getc() or fgetc() should be used

instead.

Because of possible differences in word length and byte ordering, ﬁles written using putw()

are machine-

dependent, and may be unreadable by

getw() on a different processor.

Reentrant Interfaces

If _REENTRANT is deﬁned before including <stdio.h>, the locked versions of the library functions for

getc() and getchar() are used by default.

getw_unlocked() is an obsolescent interface supported only for compatibility with existing DCE appli-

cations. New multithreaded applications should use

getw().