1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
|
/* libstdbuf -- a shared lib to preload to setup stdio buffering for a command
Copyright (C) 2009-2014 Free Software Foundation, Inc.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>. */
/* Written by Pádraig Brady. LD_PRELOAD idea from Brian Dessent. */
#include <config.h>
#include <stdio.h>
#include "system.h"
/* Note currently for glibc (2.3.5) the following call does not change
the buffer size, and more problematically does not give any indication
that the new size request was ignored:
setvbuf (stdout, (char*)NULL, _IOFBF, 8192);
The ISO C99 standard section 7.19.5.6 on the setvbuf function says:
... If buf is not a null pointer, the array it points to _may_ be used
instead of a buffer allocated by the setvbuf function and the argument
size specifies the size of the array; otherwise, size _may_ determine
the size of a buffer allocated by the setvbuf function. ...
Obviously some interpret the above to mean setvbuf(....,size)
is only a hint from the application which I don't agree with.
FreeBSD's libc seems more sensible in this regard. From the man page:
The size argument may be given as zero to obtain deferred optimal-size
buffer allocation as usual. If it is not zero, then except for
unbuffered files, the buf argument should point to a buffer at least size
bytes long; this buffer will be used instead of the current buffer. (If
the size argument is not zero but buf is NULL, a buffer of the given size
will be allocated immediately, and released on close. This is an extension
to ANSI C; portable code should use a size of 0 with any NULL buffer.)
--------------------
Another issue is that on glibc-2.7 the following doesn't buffer
the first write if it's greater than 1 byte.
setvbuf(stdout,buf,_IOFBF,127);
Now the POSIX standard says that "allocating a buffer of size bytes does
not necessarily imply that all of size bytes are used for the buffer area".
However I think it's just a buggy implementation due to the various
inconsistencies with write sizes and subsequent writes. */
static const char *
fileno_to_name (const int fd)
{
const char *ret = NULL;
switch (fd)
{
case 0:
ret = "stdin";
break;
case 1:
ret = "stdout";
break;
case 2:
ret = "stderr";
break;
default:
ret = "unknown";
break;
}
return ret;
}
static void
apply_mode (FILE *stream, const char *mode)
{
char *buf = NULL;
int setvbuf_mode;
size_t size = 0;
if (*mode == '0')
setvbuf_mode = _IONBF;
else if (*mode == 'L')
setvbuf_mode = _IOLBF; /* FIXME: should we allow 1ML */
else
{
setvbuf_mode = _IOFBF;
verify (SIZE_MAX <= ULONG_MAX);
size = strtoul (mode, NULL, 10);
if (size > 0)
{
if (!(buf = malloc (size))) /* will be freed by fclose() */
{
/* We could defer the allocation to libc, however since
glibc currently ignores the combination of NULL buffer
with non zero size, we'll fail here. */
fprintf (stderr,
_("failed to allocate a %" PRIuMAX
" byte stdio buffer\n"), (uintmax_t) size);
return;
}
}
else
{
fprintf (stderr, _("invalid buffering mode %s for %s\n"),
mode, fileno_to_name (fileno (stream)));
return;
}
}
if (setvbuf (stream, buf, setvbuf_mode, size) != 0)
{
fprintf (stderr, _("could not set buffering of %s to mode %s\n"),
fileno_to_name (fileno (stream)), mode);
free (buf);
}
}
/* Use __attribute to avoid elision of __attribute__ on SUNPRO_C etc. */
static void __attribute ((constructor))
stdbuf (void)
{
char *e_mode = getenv ("_STDBUF_E");
char *i_mode = getenv ("_STDBUF_I");
char *o_mode = getenv ("_STDBUF_O");
if (e_mode) /* Do first so can write errors to stderr */
apply_mode (stderr, e_mode);
if (i_mode)
apply_mode (stdin, i_mode);
if (o_mode)
apply_mode (stdout, o_mode);
}
|
