Date: Thu, 4 Aug 2011 19:19:28 +0200 From: Jeremie Le Hen <jeremie@le-hen.org> To: freebsd-hackers@FreeBSD.org Cc: jhb@FreeBSD.org Subject: [RFC] stdbuf: Force stdio's streams initial buffering mode (patch) Message-ID: <20110804171928.GB96031@felucia.tataz.chchile.org> In-Reply-To: <20110219185043.GA6573@felucia.tataz.chchile.org>
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On Sat, Feb 19, 2011 at 07:50:43PM +0100, Jeremie Le Hen wrote:
> I've been annoyed multiple time when running a command such like
> iostat -x 1 | grep -v ad10 | cat -n
>
> The problem stems from two factors:
> - grep's stdio sees that its stdout is not a terminal, so stdout is
> full buffered and not line-buffered;
> - iostat produces output too slowly so the aforementioned buffer takes
> numerous seconds to be filled and flushed to the last command.
>
> This problems is not specific to FreeBSD, it is actually a consequence
> of POSIX specification. I've checked this on Solaris and Linux.
>
> I've attached a small patch for stdio, so if the environment variable
> STDIO_IOLBF is set, the output streams will be line-oriented by default.
> iostat -x 1 | env STDIO_IOLBF=1 grep -v ad10 | cat -n
I improved the whole picture. Now there is a shared library
libstdbuf.so which can be loaded with LD_PRELOAD and configured through
a environment variables. It is able to initial control buffering for
stdin, stdout and stderr (no buffering, line buffering, block
buffering). There is also an utility named stdbuf(1) which can be used
to run a command with the appropriate environment variables. Those are
named after a similar tool in recent versions of GNU coreutils; of
course, I also borrowed the interface for POLA.
Here is how to use it (example taken from the manpage):
vmstat 1 | stdbuf -o L awk '$2 > 1 || $3 > 1' | cat -n
I think that using a preloaded shared library is better performance-wise
because libc doesn't bother looking up configuration variables in the
environment upon each execve(2), especially for something which is to be
rarely used.
Manpages for both stdbuf(1) and libstdbuf(3) are provided. There is
surely room for improvement, so feel free to propose corrections to
them.
The patch can be applied as-is I think, although I've developped it
against an old -CURRENT source tree (about 6 months ago).
I'm looking for some feedback and review and hopefully this feature will
be committed for FreeBSD 9.0-RELEASE.
Regards,
--
Jeremie Le Hen
Humans are born free and equal. But some are more equal than others.
Coluche
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diff -urNp src.HEAD_20111506/lib/libc/stdio/setbuf.3 src/lib/libc/stdio/setbuf.3
--- src.HEAD_20111506/lib/libc/stdio/setbuf.3 2007-01-09 01:28:07.000000000 +0100
+++ src/lib/libc/stdio/setbuf.3 2011-08-04 19:00:49.000000000 +0200
@@ -30,7 +30,7 @@
.\" SUCH DAMAGE.
.\"
.\" @(#)setbuf.3 8.1 (Berkeley) 6/4/93
-.\" $FreeBSD: src/lib/libc/stdio/setbuf.3,v 1.17 2007/01/09 00:28:07 imp Exp $
+.\" $FreeBSD: src/lib/libc/stdio/setbuf.3,v 1.17.10.1 2009/08/03 08:13:06 kensmith Exp $
.\"
.Dd June 4, 1993
.Dt SETBUF 3
@@ -83,6 +83,9 @@ normally does) it is line buffered.
The standard error stream
.Dv stderr
is always unbuffered.
+Note that these defaults maybe be altered using the
+.Xr stdbuf 1
+utility.
.Pp
The
.Fn setvbuf
@@ -177,6 +180,7 @@ function returns what the equivalent
.Fn setvbuf
would have returned.
.Sh SEE ALSO
+.Xr stdbuf 1 ,
.Xr fclose 3 ,
.Xr fopen 3 ,
.Xr fread 3 ,
diff -urNp src.HEAD_20111506/lib/libstdbuf/Makefile src/lib/libstdbuf/Makefile
--- src.HEAD_20111506/lib/libstdbuf/Makefile 1970-01-01 01:00:00.000000000 +0100
+++ src/lib/libstdbuf/Makefile 2011-08-04 18:49:59.000000000 +0200
@@ -0,0 +1,15 @@
+# $FreeBSD: src/lib/libftpio/Makefile,v 1.17.2.1 2009/08/03 08:13:06 kensmith Exp $
+
+.include <bsd.own.mk>
+
+LIB= stdbuf
+SRCS= stdbuf.c
+SHLIB_MAJOR= 1
+MAN= libstdbuf.3
+
+CFLAGS+= -I${.CURDIR}
+LDADD= -lutil
+
+WARNS?= 6
+
+.include <bsd.lib.mk>
diff -urNp src.HEAD_20111506/lib/libstdbuf/libstdbuf.3 src/lib/libstdbuf/libstdbuf.3
--- src.HEAD_20111506/lib/libstdbuf/libstdbuf.3 1970-01-01 01:00:00.000000000 +0100
+++ src/lib/libstdbuf/libstdbuf.3 2011-08-04 18:47:04.000000000 +0200
@@ -0,0 +1,111 @@
+.\" Copyright (c) 2011 Jeremie Le Hen
+.\" All rights reserved.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\" notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\" notice, this list of conditions and the following disclaimer in the
+.\" documentation and/or other materials provided with the distribution.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+.\" SUCH DAMAGE.
+.\"
+.\" $FreeBSD$
+.\"
+.Dd August 4, 2011
+.Dt LIBSTDBUF 3
+.Os
+.Sh NAME
+.Nm libstdbuf
+.Nd preloaded library to change standard streams initial buffering
+.Sh DESCRIPTION
+The
+.Nm
+library is meant to be preloaded with the
+.Ev LD_PRELOAD
+environment variable to as to change the initial buffering
+of standard input, standard output and standard error streams.
+.Pp
+Although you may load and configure this library manually,
+an utility,
+.Xr stdbuf 1 ,
+can be used to run a command with the appropriate environment variables.
+.Sh ENVIRONMENT
+Each stream can be configured indepentently through the following
+environment variables (values are defined below):
+.Bl -tag -width size -offset indent
+.It Ev STDBUF_0
+Initial buffering definition for the standard input stream
+.It Ev STDBUF_1
+Initial buffering definition for the standard output stream
+.It Ev STDBUF_2
+Initial buffering definition for the standard error stream
+.It Ev _STDBUF_I
+GNU-compatible variable for
+.Ev STDBUF_0
+.It Ev _STDBUF_O
+GNU-compatible variable equivalent to
+.Ev STDBUF_1
+.It Ev _STDBUF_E
+GNU-compatible variable equivalent to
+.Ev STDBUF_2
+.El
+.Pp
+Each variable may take one of the following values:
+.Bl -tag -width size -offset indent
+.It Qq 0
+unbuffered
+.It Qq L
+line buffered
+.It Qq B
+fully buffered with the default buffer size
+.It Ar size
+fully buffered with a buffer of
+.Ar size
+bytes
+.El
+.Sh EXAMPLE
+In the following example, the stdout stream of the
+.Xr awk 1
+command
+will be fully buffered by default because it does not refer
+to a terminal.
+.Nm
+is used to force it to be line-buffered so
+.Xr vmstat 8 Ns 's
+output will not stall until the full buffer fills.
+.Bd -literal -offset indent
+# vmstat 1 | LD_PRELOAD=/usr/lib/libstdbuf.so \\
+ STDBUF_1=L awk '$2 > 1 || $3 > 1' | cat -n
+.Ed
+.Pp
+See also the manpage of
+.Xr stdbuf 1
+for a simpler way to do this.
+.Sh HISTORY
+The
+.Nm
+library first appeared in
+.Fx 9.0 .
+.Sh AUTHORS
+.An -nosplit
+The original idea of the
+.Nm
+command comes from
+.An Padraig Brady
+who implemented it in the GNU coreutils.
+.An Jeremie Le Hen
+implemented it on
+.Fx .
diff -urNp src.HEAD_20111506/lib/libstdbuf/stdbuf.c src/lib/libstdbuf/stdbuf.c
--- src.HEAD_20111506/lib/libstdbuf/stdbuf.c 1970-01-01 01:00:00.000000000 +0100
+++ src/lib/libstdbuf/stdbuf.c 2011-08-04 18:17:07.000000000 +0200
@@ -0,0 +1,105 @@
+/*-
+ * Copyright (c) 2011 Jeremie Le Hen
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ * $FreeBSD$
+ */
+
+#include <err.h>
+#include <errno.h>
+#include <limits.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <libutil.h>
+
+static const char *
+stream_name(FILE *s)
+{
+ if (s == stdin)
+ return "stdin";
+ if (s == stdout)
+ return "stdout";
+ if (s == stderr)
+ return "stderr";
+ /* This should not happen. */
+ abort();
+}
+
+static void
+change_buf(FILE *s, const char *bufmode)
+{
+ size_t bufsiz;
+ uint64_t sizearg;
+ int mode;
+
+ bufsiz = 0;
+ if (bufmode[0] == '0' && bufmode[1] == '\0')
+ mode = _IONBF;
+ else if (bufmode[0] == 'L' && bufmode[1] == '\0')
+ mode = _IOLBF;
+ else if (bufmode[0] == 'B' && bufmode[1] == '\0') {
+ mode = _IOFBF;
+ bufsiz = 0;
+ } else {
+ errno = 0;
+ if (expand_number(bufmode, &sizearg) == -1) {
+ warn("Wrong buffer mode '%s' for %s", bufmode,
+ stream_name(s));
+ return;
+ }
+ if (sizearg > SIZE_T_MAX) {
+ warn("Buffer size too big for %s", stream_name(s));
+ return;
+ }
+ mode = _IOFBF;
+ bufsiz = (size_t)sizearg;
+ }
+ if (setvbuf(s, NULL, mode, bufsiz) != 0)
+ warn("Cannot set buffer mode '%s' for %s", bufmode,
+ stream_name(s));
+}
+
+__attribute__ ((constructor)) static void
+stdbuf(void)
+{
+ char *i_mode, *o_mode, *e_mode;
+
+ i_mode = getenv("STDBUF_0");
+ if (i_mode == NULL)
+ i_mode = getenv("_STDBUF_I");
+ o_mode = getenv("STDBUF_1");
+ if (o_mode == NULL)
+ o_mode = getenv("_STDBUF_O");
+ e_mode = getenv("STDBUF_2");
+ if (e_mode == NULL)
+ e_mode = getenv("_STDBUF_E");
+
+ if (e_mode)
+ change_buf(stderr, e_mode);
+ if (i_mode)
+ change_buf(stdin, i_mode);
+ if (o_mode)
+ change_buf(stdout, o_mode);
+}
diff -urNp src.HEAD_20111506/usr.bin/stdbuf/Makefile src/usr.bin/stdbuf/Makefile
--- src.HEAD_20111506/usr.bin/stdbuf/Makefile 1970-01-01 01:00:00.000000000 +0100
+++ src/usr.bin/stdbuf/Makefile 2011-08-02 19:16:30.000000000 +0200
@@ -0,0 +1,8 @@
+# $Id$
+
+PROG= stdbuf
+SRCS= stdbuf.c
+
+WARNS?= 6
+
+.include <bsd.prog.mk>
Files src.HEAD_20111506/usr.bin/stdbuf/sh.core and src/usr.bin/stdbuf/sh.core differ
diff -urNp src.HEAD_20111506/usr.bin/stdbuf/stdbuf.1 src/usr.bin/stdbuf/stdbuf.1
--- src.HEAD_20111506/usr.bin/stdbuf/stdbuf.1 1970-01-01 01:00:00.000000000 +0100
+++ src/usr.bin/stdbuf/stdbuf.1 2011-08-04 18:46:35.000000000 +0200
@@ -0,0 +1,124 @@
+.\" Copyright (C) 2011 Jeremie Le Hen
+.\" All rights reserved.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code and documentation must retain the above
+.\" copyright notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\" notice, this list of conditions and the following disclaimer in the
+.\" documentation and/or other materials provided with the distribution.
+.\" 3. All advertising materials mentioning features or use of this software
+.\" must display the following acknowledgement:
+.\" This product includes software developed or owned by Caldera
+.\" International, Inc.
+.\" 4. Neither the name of Caldera International, Inc. nor the names of other
+.\" contributors may be used to endorse or promote products derived from
+.\" this software without specific prior written permission.
+.\"
+.\" USE OF THE SOFTWARE PROVIDED FOR UNDER THIS LICENSE BY CALDERA
+.\" INTERNATIONAL, INC. AND CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR
+.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+.\" IN NO EVENT SHALL CALDERA INTERNATIONAL, INC. BE LIABLE FOR ANY DIRECT,
+.\" INDIRECT INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+.\" (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+.\" SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+.\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
+.\" IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+.\" POSSIBILITY OF SUCH DAMAGE.
+.\"
+.\" $FreeBSD: src/usr.bin/dc/dc.1,v 1.2 2010/01/22 23:50:46 delphij Exp $
+.\"
+.Dd August 4, 2011
+.Dt STDBUF 1
+.Os
+.Sh NAME
+.Nm stdbuf
+.Nd change standard streams initial buffering
+.Sh SYNOPSIS
+.Nm
+.Op Fl e Ar bufdef
+.Op Fl i Ar bufdef
+.Op Fl o Ar bufdef
+.Op Ar command Op ...
+.Sh DESCRIPTION
+.Nm
+is used to change the initial buffering of standard input,
+standard output and/or standard error streams for
+.Ar command .
+It relies on
+.Xr libstdbuf 3
+which is loaded and configured by
+.Nm
+through environment variables.
+.Pp
+The options are as follows:
+.Bl -tag -width Ds
+.It Fl e Ar bufdef
+Set initial buffering of the standard error stream for
+.Ar command
+as defined by
+.Ar bufdef
+.Pq see Sx BUFFER DEFINITION .
+.It Fl i Ar bufdef
+Set initial buffering of the standard input stream for
+.Ar command
+as defined by
+.Ar bufdef
+.Pq see Sx BUFFER DEFINITION .
+.It Fl o Ar bufdef
+Set initial buffering of the standard output stream for
+.Ar command
+as defined by
+.Ar bufdef
+.Pq see Sx BUFFER DEFINITION .
+.El
+.Sh BUFFER DEFINITION
+Buffer definition is the same as in
+.Xr libstdbuf 3 :
+.Bl -tag -width size -offset indent
+.It Qq 0
+unbuffered
+.It Qq L
+line buffered
+.It Qq B
+fully buffered with the default buffer size
+.It Ar size
+fully buffered with a buffer of
+.Ar size
+bytes
+.El
+.Sh EXAMPLES
+In the following example, the stdout stream of the
+.Xr awk 1
+command
+will be fully buffered by default because it does not refer
+to a terminal.
+.Nm
+is used to force it to be line-buffered so
+.Xr vmstat 8 Ns 's
+output will not stall until the full buffer fills.
+.Bd -literal -offset indent
+# vmstat 1 | stdbuf -o L awk '$2 > 1 || $3 > 1' | cat -n
+.Ed
+.Sh SEE ALSO
+.Xr libstdbuf 3 ,
+.Xr setvbuf 3
+.Sh HISTORY
+The
+.Nm
+utility first appeared in
+.Fx 9.0 .
+.Sh AUTHORS
+.An -nosplit
+The original idea of the
+.Nm
+command comes from
+.An Padraig Brady
+who implemented it in the GNU coreutils.
+.An Jeremie Le Hen
+implemented it on
+.Fx .
diff -urNp src.HEAD_20111506/usr.bin/stdbuf/stdbuf.c src/usr.bin/stdbuf/stdbuf.c
--- src.HEAD_20111506/usr.bin/stdbuf/stdbuf.c 1970-01-01 01:00:00.000000000 +0100
+++ src/usr.bin/stdbuf/stdbuf.c 2011-08-04 18:17:50.000000000 +0200
@@ -0,0 +1,107 @@
+/*-
+ * Copyright (c) 2011 Jeremie Le Hen
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ * $FreeBSD$
+ */
+
+#include <err.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+#define LIBSTDBUF "/usr/lib/libstdbuf.so"
+
+extern char *__progname;
+
+static void usage(int);
+
+static void
+usage(int s)
+{
+
+ fprintf(stderr, "Usage: %s [-e bufdef] [-i bufdef] [-o bufdef] "
+ "<command> [args ...]\n", __progname);
+ fprintf(stderr, " ``bufdef'' being:\n");
+ fprintf(stderr, " - \"0\" to disable buffering;\n");
+ fprintf(stderr, " - \"L\" to set line-buffering;\n");
+ fprintf(stderr, " - <size> to set full-buffering.\n");
+ exit(s);
+}
+
+int
+main(int argc, char *argv[])
+{
+ int i;
+ char *ibuf = NULL, *obuf = NULL, *ebuf = NULL;
+ char *preload0, *preload1;
+
+ while ((i = getopt(argc, argv, ":e:i:o:")) != -1) {
+ switch (i) {
+ case 'e':
+ ebuf = optarg;
+ break;
+ case 'i':
+ ibuf = optarg;
+ break;
+ case 'o':
+ obuf = optarg;
+ break;
+ case ':':
+ warnx("Missing argument for option -%c", optopt);
+ usage(1);
+ break;
+ case '?':
+ default:
+ warnx("Unknown option -%c", optopt);
+ usage(1);
+ break;
+ }
+ }
+ argc -= optind;
+ argv += optind;
+
+ if (ibuf != NULL && setenv("STDBUF_0", ibuf, 1) == -1)
+ warn("Failed to set environment variable: %s=%s",
+ "STDBUF_0", ibuf);
+ if (obuf != NULL && setenv("STDBUF_1", obuf, 1) == -1)
+ warn("Failed to set environment variable: %s=%s",
+ "STDBUF_1", obuf);
+ if (ebuf != NULL && setenv("STDBUF_2", ebuf, 1) == -1)
+ warn("Failed to set environment variable: %s=%s",
+ "STDBUF_2", ebuf);
+
+ preload0 = getenv("LD_PRELOAD");
+ if (preload0 == NULL)
+ i = asprintf(&preload1, "LD_PRELOAD=" LIBSTDBUF);
+ else
+ i = asprintf(&preload1, "LD_PRELOAD=%s:%s", preload0,
+ LIBSTDBUF);
+
+ if (i < 0 || putenv(preload1) == -1)
+ warn("Failed to set environment variable: %s", preload1);
+
+ execvp(argv[0], argv);
+ err(2, "%s", argv[0]);
+}
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