INTRO(3S) UNIX Programmer's Manual INTRO(3S) NAME stdio - standard buffered input/output package SYNOPSIS #include FILE *stdin; FILE *stdout; FILE *stderr; DESCRIPTION The functions described in section 3S constitute a user- level buffering scheme. The in-line macros _g_e_t_c and _p_u_t_c(3S) handle characters quickly. The higher level rou- tines _g_e_t_s, _f_g_e_t_s, _s_c_a_n_f, _f_s_c_a_n_f, _f_r_e_a_d, _p_u_t_s, _f_p_u_t_s, _p_r_i_n_t_f, _f_p_r_i_n_t_f, _f_w_r_i_t_e all use _g_e_t_c and _p_u_t_c; they can be freely intermixed. A file with associated buffering is called a _s_t_r_e_a_m, and is declared to be a pointer to a defined type FILE. _F_o_p_e_n(3S) creates certain descriptive data for a stream and returns a pointer to designate the stream in all further transactions. There are three normally open streams with constant pointers declared in the include file and associated with the stan- dard open files: stdin standard input file stdout standard output file stderr standard error file A constant `pointer' NULL (0) designates no stream at all. An integer constant EOF (-1) is returned upon end of file or error by integer functions that deal with streams. Any routine that uses the standard input/output package must include the header file <_s_t_d_i_o._h> of pertinent macro defini- tions. The functions and constants mentioned in sections labeled 3S are declared in the include file and need no further declaration. The constants, and the following `functions' are implemented as macros; redeclaration of these names is perilous: _g_e_t_c, _g_e_t_c_h_a_r, _p_u_t_c, _p_u_t_c_h_a_r, _f_e_o_f, _f_e_r_r_o_r, _f_i_l_e_n_o. SEE ALSO close(2), open(2), read(2), write(2), f*(3S) DIAGNOSTICS The value EOF is returned uniformly to indicate that a FILE pointer has not been initialized with _f_o_p_e_n, input (output) has been attempted on an output (input) stream, or a FILE pointer designates corrupt or otherwise unintelligible FILE Printed 7/31/83 1 INTRO(3S) UNIX Programmer's Manual INTRO(3S) data. For purposes of efficiency, this implementation of the stan- dard library has been changed to line buffer output to a terminal by default and attempts to do this transparently by flushing the output whenever a _r_e_a_d(2) from the standard input is necessary. This is almost always transparent, but may cause confusion or malfunctioning of programs which use standard i/o routines but use _r_e_a_d(2) themselves to read from the standard input. In cases where a large amount of computation is done after printing part of a line on an output terminal, it is neces- sary to _f_f_l_u_s_h(3S) the standard output before going off and computing so that the output will appear. BUGS The standard buffered functions do not interact well with certain other library and system functions, especially _v_f_o_r_k and _a_b_o_r_t. LIST OF FUNCTIONS _N_a_m_e _A_p_p_e_a_r_s _o_n _P_a_g_e _D_e_s_c_r_i_p_t_i_o_n 9 clearerr ferror.3s stream status inquiries fclose fclose.3s close or flush a stream feof ferror.3s stream status inquiries ferror ferror.3s stream status inquiries fflush fclose.3s close or flush a stream fgetc getc.3s get character or word from stream fgets gets.3s get a string from a stream fileno ferror.3s stream status inquiries fprintf printf.3s formatted output conversion fputc putc.3s put character or word on a stream fputs puts.3s put a string on a stream fread fread.3s buffered binary input/output fscanf scanf.3s formatted input conversion fseek fseek.3s reposition a stream ftell fseek.3s reposition a stream fwrite fread.3s buffered binary input/output getc getc.3s get character or word from stream getchar getc.3s get character or word from stream gets gets.3s get a string from a stream getw getc.3s get character or word from stream pclose popen.3s initiate I/O to/from a process popen popen.3s initiate I/O to/from a process printf printf.3s formatted output conversion putc putc.3s put character or word on a stream putchar putc.3s put character or word on a stream puts puts.3s put a string on a stream putw putc.3s put character or word on a stream rewind fseek.3s reposition a stream scanf scanf.3s formatted input conversion Printed 7/31/83 2 9 INTRO(3S) UNIX Programmer's Manual INTRO(3S) setbuf setbuf.3s assign buffering to a stream sprintf printf.3s formatted output conversion sscanf scanf.3s formatted input conversion system system.3s issue a shell command ungetc ungetc.3s push character back into input stream Printed 7/31/83 3