SETBUF(3) 1989 SETBUF(3) NNAAMMEE setbuf, setbuffer, setlinebuf - assign buffering to a stream SSYYNNOOPPSSIISS ##iinncclluuddee <<ssttddiioo..hh>> sseettbbuuff((ssttrreeaamm,, bbuuff)) FFIILLEE **ssttrreeaamm;; cchhaarr **bbuuff;; sseettbbuuffffeerr((ssttrreeaamm,, bbuuff,, ssiizzee)) FFIILLEE **ssttrreeaamm;; cchhaarr **bbuuff;; iinntt ssiizzee;; sseettlliinneebbuuff((ssttrreeaamm)) FFIILLEE **ssttrreeaamm;; DDEESSCCRRIIPPTTIIOONN The three types of buffering available are unbuffered, block buffered, and line buffered. When an output stream is unbuffered, information appears on the destination file or terminal as soon as written; when it is block buffered many characters are saved up and written as a block; when it is line buffered characters are saved up until a newline is encountered or input is read from stdin. _F_f_l_u_s_h (see _f_c_l_o_s_e(3)) may be used to force the block out early. Nor- mally all files are block buffered. A buffer is obtained from _m_a_l_l_o_c(3) upon the first _g_e_t_c or _p_u_t_c(3) on the file. If the standard stream ssttddoouutt refers to a terminal it is line buffered. The standard stream ssttddeerrrr is always unbuf- fered. _S_e_t_b_u_f is used after a stream has been opened but before it is read or written. The character array _b_u_f is used instead of an automatically allocated buffer. If _b_u_f is the con- stant pointer NNUULLLL,, input/output will be completely unbuf- fered. A manifest constant BBUUFFSSIIZZ tells how big an array is needed: cchhaarr buf[BUFSIZ]; _S_e_t_b_u_f_f_e_r, an alternate form of _s_e_t_b_u_f, is used after a stream has been opened but before it is read or written. The character array _b_u_f whose size is determined by the _s_i_z_e argument is used instead of an automatically allocated buffer. If _b_u_f is the constant pointer NNUULLLL, input/output will be completely unbuffered. _S_e_t_l_i_n_e_b_u_f is used to change _s_t_d_o_u_t or _s_t_d_e_r_r from block buffered or unbuffered to line buffered. Unlike _s_e_t_b_u_f and _s_e_t_b_u_f_f_e_r it can be used at any time that the file Printed 7/27/90 April 1 SETBUF(3) 1989 SETBUF(3) descriptor is active. A file can be changed from unbuffered or line buffered to block buffered by using _f_r_e_o_p_e_n (see _f_o_p_e_n(3)). A file can be changed from block buffered or line buffered to unbuf- fered by using _f_r_e_o_p_e_n followed by _s_e_t_b_u_f with a buffer argument of NNUULLLL. SSEEEE AALLSSOO fopen(3), getc(3), putc(3), malloc(3), fclose(3), puts(3), printf(3), fread(3) BBUUGGSS The _s_e_t_b_u_f_f_e_r and _s_e_t_l_i_n_e_b_u_f functions are not portable to non-4.2BSD versions of UNIX. On 4.2BSD and 4.3BSD systems, _s_e_t_b_u_f always uses a suboptimal buffer size and should be avoided. _S_e_t_b_u_f_f_e_r is not usually needed as the default file I/O buffer sizes are optimal. Printed 7/27/90 April 2