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Annotation of cci/usr/src/man/man3/setbuf.3s, revision 1.1.1.1

1.1       root        1: .TH SETBUF 3S  "19 January 1983"
                      2: .UC 4
                      3: .SH NAME
                      4: setbuf, setbuffer, setlinebuf \- assign buffering to a stream
                      5: .SH SYNOPSIS
                      6: .B #include <stdio.h>
                      7: .PP
                      8: .B setbuf(stream, buf)
                      9: .br
                     10: .SM
                     11: .B FILE
                     12: .B *stream;
                     13: .br
                     14: .B char *buf;
                     15: .PP
                     16: .B setbuffer(stream, buf, size)
                     17: .br
                     18: .SM
                     19: .B FILE
                     20: .B *stream;
                     21: .br
                     22: .B char *buf;
                     23: .br
                     24: .B int size;
                     25: .PP
                     26: .B setlinebuf(stream)
                     27: .br
                     28: .SM
                     29: .B FILE
                     30: .B *stream;
                     31: .SH DESCRIPTION
                     32: The three types of buffering available are unbuffered, block buffered,
                     33: and line buffered.
                     34: When an output stream is unbuffered, information appears on the
                     35: destination file or terminal as soon as written;
                     36: when it is block buffered many characters are saved up and written as a block;
                     37: when it is line buffered characters are saved up until a newline is
                     38: encountered or input is read from stdin.
                     39: .I Fflush
                     40: (see 
                     41: .IR fclose (3S))
                     42: may be used to force the block out early.
                     43: Normally all files are block buffered.
                     44: A buffer is obtained from
                     45: .IR  malloc (3)
                     46: upon the first
                     47: .I getc
                     48: or
                     49: .IR  putc (3S)
                     50: on the file.
                     51: If the standard stream
                     52: .B stdout
                     53: refers to a terminal it is line buffered.
                     54: The standard stream
                     55: .B stderr
                     56: is always unbuffered.
                     57: .PP
                     58: .I Setbuf
                     59: is used after a stream has been opened but before it is read or written.
                     60: The character array
                     61: .I buf
                     62: is used instead of an automatically allocated buffer.  If
                     63: .I buf
                     64: is the constant pointer
                     65: .SM
                     66: .B NULL,
                     67: input/output will be completely unbuffered.
                     68: A manifest constant 
                     69: .SM
                     70: .B BUFSIZ
                     71: tells how big an array is needed:
                     72: .IP
                     73: .B char
                     74: buf[BUFSIZ];
                     75: .PP
                     76: .IR Setbuffer ,
                     77: an alternate form of 
                     78: .IR setbuf ,
                     79: is used after a stream has been opened but before it is read or written.
                     80: The character array
                     81: .I buf
                     82: whose size is determined by the 
                     83: .I size
                     84: argument is used instead of an automatically allocated buffer.  If
                     85: .I buf
                     86: is the constant pointer
                     87: .SM
                     88: .BR NULL ,
                     89: input/output will be completely unbuffered.
                     90: .PP
                     91: .I Setlinebuf
                     92: is used to change
                     93: .I stdout
                     94: or
                     95: .I stderr
                     96: from block buffered or unbuffered to line buffered.
                     97: Unlike
                     98: .I setbuf
                     99: and
                    100: .I setbuffer
                    101: it can be used at any time that the file descriptor is active.
                    102: .PP
                    103: A file can be changed from unbuffered or line buffered to block buffered
                    104: by using
                    105: .I freopen
                    106: (see
                    107: .IR fopen (3S)).
                    108: A file can be changed from block buffered or line buffered to unbuffered
                    109: by using
                    110: .I freopen
                    111: followed by
                    112: .I setbuf
                    113: with a buffer argument of 
                    114: .SM
                    115: .BR NULL .
                    116: .SH "SEE ALSO"
                    117: fopen(3S),
                    118: getc(3S),
                    119: putc(3S),
                    120: malloc(3),
                    121: fclose(3S),
                    122: puts(3S),
                    123: printf(3S),
                    124: fread(3S)
                    125: .SH BUGS
                    126: The standard error stream should be line buffered by default.
                    127: .LP
                    128: The
                    129: .I setbuffer
                    130: and
                    131: .I setlinebuf
                    132: functions are not portable to non 4.2 BSD versions of UNIX.

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