putc, putc_unlocked - put byte on stream

Syntax	#include <stdio.h> int putc(int c, FILE *stream); int putc_unlocked(int c, FILE *stream);
Description	The function putc() is equivalent to fputc(), but is defined as a macro and a function. When it is used as a macro, it may evaluate c and stream more than once, so these argument should never be an expression with side-effects. The function putc_unlocked() (see "getc_unlocked, getchar_unlocked, putc_unlocked, putchar_unlocked - standard I/O with explicit lock by the client" under getc_unlocked( ) ...) is functionally equivalent to putc() except that it’s implementation is not thread-safe. For this reason it can only be used safely in a multithreaded program if the thread that calls it owns the corresponding (FILE *) object. This is the case after successfully calling the flockfile() or ftrylockfile() functions.
Return val.	See fputc().
Errors	See fputc().
Notes	If putc() is used as a macro, it may handle the arguments c and stream with side-effects incorrectly. putc(c, *f++), in particular, will usually not work correctly. It is therefore advisable to use fputc() instead. The bytes are not written immediately to the external file but are stored in an internal C buffer (see section “Buffering streams”). The program environment determines whether putc() is executed for a BS2000 or POSIX file. BS2000 Control characters for white space (\n, \t, etc.) are converted to their appropriate effect when output to text files, depending on the type of text file (see section “White-spacecharacters”). (End)
See also	fputc(), getc_unlocked(), stdio.h.