Read Me(libexplain) Read Me(libexplain)
NAME
libexplain - Explain errno values returned by libc functions
DESCRIPTION
The libexplain package provides a library which may be used to explain
Unix and Linux system call errors. This will make your application's
error messages much more informative to your users.
The library is not quite a drop-in replacement for strerror(3), but it
comes close. Each system call has a dedicated libexplain function, for
example
fd = open(path, flags, mode);
if (fd < 0)
{
fprintf(stderr, "%s\n", explain_open(path, flags, mode));
exit(EXIT_FAILURE);
}
If, for example, you were to try to open no-such-dir/some-file, you
would see a message like
open(pathname = "no-such-dir/some-file", flags = O_RDONLY)
failed, No such file or directory (2, ENOENT) because there is
no "no-such-dir" directory in the current directory
The good new is that for each of these functions there is a wrapper
function, in this case explain_open_or_die(3), that includes the above
code fragment. Adding good error reporting is as simple as using a
different, but similarly named, function. The library also provides
thread safe variants of each explanation function.
Coverage includes 171 system calls and 547 ioctl requests.
Tutorial Documentation
There is a paper available in PDF format
(http://libexplain.sourceforge.net/lca2010/lca2010.pdf) that describes
the library and how to use LibExplain. The paper can also be accessed
as explain_lca2010(1), which also appears in the reference manual (see
below).
HOME PAGE
The latest version of libexplain is available on the Web from:
URL: http://libexplain.sourceforge.net/
File: index.html # the libexplain page
File: libexplain.0.48.README # Description, from the tar file
File: libexplain.0.48.lsm # Description, LSM format
File: libexplain.0.48.tar.gz # the complete source
File: libexplain.0.48.pdf # Reference Manual
BUILDING LIBEXPLAIN
Full instructions for building libexplain may be found in the BUILDING
file included in this distribution.
COPYRIGHT
libexplain version 0.48
Copyright (C) 2008, 2009, 2010, 2011 Peter Miller
Library License
The shared library, and its include files, are GNU LGPL licensed.
This program is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this program. If not, see
<http://www.gnu.org/licenses/>.
Non-Library License
Everything else (all source files that do not constitute the shared
library and its include files) are GNU GPL licensed.
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/>.
AUTHOR
Peter Miller E-Mail: pmiller@opensource.org.au
/\/\* WWW: http://www.canb.auug.org.au/~millerp/
RELEASE NOTES
This section details the various features and bug fixes of the various
releases. For excruciating and complete detail, and also credits for
those of you who have generously sent me suggestions and bug reports,
see the etc/CHANGES.* files.
Coverage includes 171 system calls and 547 ioctl requests.
Version 0.48 (2011-Nov-08)
* Explanations are now available for errors reported by the shmat(2)
system call.
* Several build problems on Solaris have been fixed.
* Dagobert Michelsen <dam@opencsw.org> found the test 625 was throwing
a false negative in his test environment. It can now cope with stdin
being closed.
* Dagobert Michelsen <dam@opencsw.org> discovered that, on Solaris,
test false negatives were caused by the need for a space before the
width in a "fmt -w 800" command.
* Eric Smith <eric@brouhaha.com> discovered that lsof(1) could report
errors as executable names, when it couldn't read the symlink. These
non-results are now filtered out.
* Eric Smith <eric@brouhaha.com> discovered three false negatives from
tests of the kill(2) system call.
* Better explanations are now available when a user attempts to execute
a directory.
Version 0.47 (2011-Sep-27)
* Explanations are now available for errors reported by the setsid(2)
system call.
* The Ubuntu PPA build farm found several Hardy build problems. These
have been fixed.
* Code has been added to detect those cases where a file descriptor may
be open for reading and writing, but the I/O stream it is accessed by
is only open for one of them.
* Code has been added to cope with false negatives when lsof(1) is not
as helpful as could be desired.
* Michael Bienia <geser@ubuntu.com> discovered a build problem with the
SIOCSHWTSTAMP ioctl request, and sent a patch.
Version 0.46 (2011-Aug-24)
* LibExplain has been ported to Solaris 8, 9 and 10. My thanks to
Dagobert Michelsen and http://opencsw.org/ for assistance with this
port.
* Several more Linux ioctl(2) requests are supported.
* A segfault has been fixed in the output tee filter when handling
exit.
Version 0.45 (2011-Jul-17)
* Dagobert Michelsen <dam@opencsw.org> discoversed several build
problems on OpenSolaris; these have been fixed.
* Explanations are now available for errors reported by the Linux
ioctl(2) V4L1 system calls.
Version 0.44 (2011-Jul-03)
* Several build problem to do with older Linux kernels have been fixed.
Version 0.42 (2011-Jul-02)
* Explanations are now available for errors reported by the V4L2 ioctl
requests.
* The Debian package no longer installs the libtool *.la file.
Debian: Closes: 621621
* The call arguments printed for ioctl(2) now include the type of the
third argument.
* The error messages now include more information about block and
character special devices, when printing file types.
Version 0.42 (2011-May-26)
* This change set adds an "ldconfig" hint to the BUILDING instructions.
My thanks to Blake McBride <blake@arahant.com> for this suggestion.
* Emanuel Haupt <ehaupt@critical.ch> reported several problems building
libexplain on FreeBSD. These have been fixed.
Version 0.41 (2011-Mar-15)
* There were some C++ keywords in the unclude files, which caused
problems for C++ users. They have been replaced.
* Explanations are now availaible for errors reported by the
getpgid(2), getpgrp(2), ptrace(2), setgpid(2) and setpgrp(2) system
calls.
Version 0.40 (2010-Oct-05)
* The code now builds and tests successfully on FreeBSD.
* Explanations are now available for errors reported by the calloc(3)
and poll(2) system calls.
Version 0.39 (2010-Sep-12)
* A build problem has been fixed on Ubuntu Hardy, a number of symbols
are absent from older versions of <linux/cdrom.h>, conditional code
has been added for them.
* A bug has been fixed in one of the documentation files, it was
missing the conditional around the .XX macro, causing rpmlint(1) and
lintian(1) to complain.
Version 0.38 (2010-Sep-08)
* Some build problems on Fedora 13 have been fixed.
Version 0.37 (2010-Aug-27)
* The library source files are supposed to be LGPL, however over 1000
of them were GPL (about 20%). This has been fixed.
* A couple of problems building on Fedora 13 have been fixed.
Version 0.36 (2010-Aug-25)
* Several false negative reported by tests on the Linux "alpha" and
"ia64" architectures have been fixed.
Version 0.35 (2010-Aug-15)
* A number of falve negatives from tests have been fixed, primarily due
to random differences between Linux architectures.
* The BUILDING document goes into more detail about things that can
cause false negatives when testing.
* The man pages have been fixed so that they no longer contain
unescaped hyphen characters, as warned about by the lintian(1)
program.
Version 0.34 (2010-Aug-07)
* Another test 33 false negative has been fixed.
* There is a new "hanging-indent" option, that can be set from the
EXPLAIN_OPTION environment variable. It defaults to zero for
backwards compatibility. Applications may set it using the
explain_option_hanging_indent_set(3) function.
Version 0.33 (2010-Jul-04)
* A number of testing false negatives (found by the Debian build farm)
have been fixed.
* There are new explain_output_error(3) and
explain_output_error_and_die(3) functions for printing formatted
error messages.
* Some systems have mmap(2) report (void*)(-1) instead of NULL for
errors. This is now understood.
Version 0.32 (2010-Jun-22)
* Explanations are now available for errors reported by the mmap(2),
munmap(2) and utimes(2) system calls.
* A number of false negatives for tests on some less common
architectures have been fixed.
* Some build problems relating to ioctl(2) support have been fixed.
* A bug has been fixed in the libexplain/output.h file, it was missing
the C++ insulation.
Version 0.31 (2010-May-01)
* A number of build problems have been fixed.
Version 0.30 (2010-Apr-28)
* Several test false negatives have been fixed, on various Debian
architectures.
Version 0.29 (2010-Apr-25)
* A number of build problems, discovered by the Debian build farm, have
been fixed. Who would of thought that there could be some much
inconsistency between Linux architectures?
Version 0.28 (2010-Apr-19)
* Several architecture-specific build problems, found by the Debian
build farm, have been fixed.
Version 0.27 (2010-Apr-17)
* Several architecture-specific build problems, found by the Debian
build farm, have been fixed.
Version 0.26 (2010-Apr-06)
* A build problem has been fixed on systems where va_list is not
compatible with const void *
* This change set removes the unused-result warning form
explain_lseek_or_die(3), because it is very common to ignore the
result.
* Explanations are now available for errors reported by the
socketpair(2) system call.
Version 0.25 (2010-Mar-22)
* Portability of the code has been improved.
* The explain(3) man page now mentions AC_SYS_LARGEFILE in the building
requirements.
* Coverage now includes the fprintf(3), printf(3), snprintf(3),
sprintf(3), vfprintf(3), vprintf(3), vsnprintf(3) and vsprintf(3)
system calls.
Version 0.24 (2010-Mar-03)
* It is now possible to redirected libexplain output. For example, it
is now possible to redirect all output to syslog(3).
* Coverage now includes the fstatvfs(2) and statvfs(2) system call.
* A number of problems found while building and testing on Solaris have
been fixed.
Version 0.23 (2010-Feb-21)
* It turns out that on alpha architecture, you can't disambiguate the
FIBMAP vs BMP_IOCTL case in the pre-processor. The code now uses a
disambiguate function. This problem was discovered by the Debian
build farm.
Version 0.22 (2010-Feb-12)
* This change set fixes a false negative found by the Debian automated
build system.
Version 0.21 (2010-Feb-09)
* Explanations are now available for errors reported by the fpurge(3),
getw(3) and putw(3) system calls.
* Some build problems have been fixed.
Version 0.20 (2010-Jan-20)
* Several lintian warnings relating to the man pages have been fixed.
* The LIBEXPLAIN_OPTIONS environment variable now understands a new
symbolic-mode-bits=true option. It defaults to false, for shorter
error explanations.
* There is a new explain_lca2010(1) man page. This is a gentle
introduction to libexplain, and the paper accompanying my LCA 2010
talk.
* When process ID (pid) values are printed, they are now accompanied by
the name of the process executable, when available.
* Numerous build bugs and niggles have been fixed.
* Explanations are now available for errors reported by the execlp(3),
fdopendir(3), feof(3), fgetpos(3), fputs(3), fseek(3), fsetpos(3),
fsync(2), ftell(3), mkdtemp(3), mknod(2), mkostemp(3), mkstemp(3),
mktemp(3), putenv(3), puts(3), raise(3), setbuf(3), setbuffer(3),
setenv(3), setlinebuf(3), setvbuf(3), stime(2), tempnam(3),
tmpfile(3), tmpnam(3), ungetc(3), unsetenv(3) and vfork(2) system
calls.
* The ioctl requests from linux/sockios.h, linux/ext2_fs.h,
linux/if_eql.h, PPP, linux/lp.h, and linux/vt.h are now understood.
Several of the ioctl explanations have been improved.
Version 0.19 (2009-Sep-07)
* The ioctl requests from linux/hdreg.h are now understood.
* Some build problems on Debian Lenny have been fixed.
Version 0.18 (2009-Sep-05)
* More ioctl requests are understood.
* Explanations are now available for errors reported by the
tcsendbreak(3), tcsetattr(3), tcgetattr(3), tcflush(3), tcdrain(3),
system calls.
Version 0.17 (2009-Sep-03)
* Explanations are now available for errors reported by the telldir(3)
system call.
* A number of Linux build problems have been fixed.
* Explanations for a number of corner-cases of the open(2) system call
have been improved, where flags values interact with file types and
mount options.
* A number of BSD build problems have been fixed.
* More ioctl(2) commands are understood.
* A bug has been fixed in the way absolute symbolic links are processed
by the path_resolution code.
Version 0.16 (2009-Aug-03)
* The EROFS and ENOMEDIUM explanations now greatly improved.
* A number of build problems and false negatives have been fixed on
x86_64 architecture.
* The Linux floppy disk and CD-ROM ioctl requests are now supported.
* Explanations are now available for the errors reported by the
getdomainname(2), readv(2), setdomainname(2), ustat(2) and writev(2)
system calls.
Version 0.15 (2009-Jul-26)
* A number of build errors and warnings on amd64 have been fixed. The
problems were only detectable on 64-bit systems.
Version 0.14 (2009-Jul-19)
* Coverage now includes another 29 system calls: accept4(2), acct(2),
adjtime(3), adjtimex(2), chroot(2), dirfd(3), eventfd(2), fflush(3),
fileno(3), flock(2), fstatfs(2), ftime(3), getgroups(2),
gethostname(2), kill(2), nice(2), pread(2), pwrite(2),
sethostname(2), signalfd(2), strdup(3), strtod(3), strtof(3),
strtol(3), strtold(3), strtoll(3), strtoul(3), strtoull(3), and
timerfd_create(2). A total of 110 system calls are now supported
* The ./configure script no longer demands lsof(1). The Linux
libexplain code doesn't need lsof(1). On systems not supported by
lsof(1), the error messages aren't quite as useful, but libexplain
still works.
* There is now an explain_*_on_error function for each system call,
each reports errors but still returns the original return value to
the caller.
Version 0.13 (2009-May-17)
* The web site now links to a number of services provided by
SourceForge.
* Several problems have been fixed with compiling libexplain on 64-bit
systems.
Version 0.12 (2009-May-04)
* A build problem has been fixed on hosts that didn't need to do
anything special for large file support.
Version 0.11 (2009-Mar-29)
* The current directory is replaced in messages with an absolute path
in cases where the user's idea of the current directory may differ
from that of the current process.
Version 0.10 (2009-Mar-24)
* The name prefix on all of the library functions has been changed from
"libexplain_" to just "explain_". This was the most requested
change. You will need to change your code and recompile. Apologies
for the inconvenience.
Version 0.9 (2009-Feb-27)
* Two false negatives in the tests have been fixed.
* The ./configure script now explicitly looks for bison(1), and
complains if it cannot be found.
* The socket(7) address family is now decoded.
Version 0.8 (2009-Feb-14)
* A problem with the Debian packaging has been fixed.
* The decoding of IPv4 sockaddr structs has been improved.
Version 0.7 (2009-Feb-10)
* Coverage has been extended to include getsockopt(2), getpeername(2),
getsockname(2) and setsockopt(2).
* Build problems on Debian Sid have been fixed.
* More magnetic tape ioctl controls, from operating systems other than
Linux, have been added.
Version 0.6 (2009-Jan-16)
* Coverage has been extended to include execvp(3), ioctl(2), malloc(3),
pclose(3), pipe(2), popen(3) and realloc(3) system calls.
* The coverage for ioctl(2) includes linux console controls, magnetic
tape controls, socket controls, and terminal controls.
* A false negative from test 31 has been fixed.
Version 0.5 (2009-Jan-03)
* A build problem on Debian sid has been fixed.
* There is a new explain_system_success(3) function, that performs all
that explain_system_success_or_die(3) performs, except that it does
not call exit(2).
* There is more i18n support.
* A bug with the pkg-config(1) support has been fixed.
Version 0.4 (2008-Dec-24)
* Coverage now includes accept(2), bind(2), connect(2), dup2(2),
fchown(2), fdopen(3), fpathconf(2), fputc(2), futimes(2),
getaddrinfo(2), getcwd(2), getrlimit(2), listen(2), pathconf(2),
putc(2), putchar(2), select(2).
* Internationalization has been improved.
* The thread safety of the code has been improved.
* The code is now able to be compiled on OpenBSD. The test suite still
gives many false negatives, due to differences in strerror(3)
results.
Version 0.3 (2008-Nov-23)
* Cover has been extended to include closedir(3), execve(2), ferror(3),
fgetc(3), fgets(3), fork(2), fread(3), getc(3), gettimeofday(2),
lchown(2), socket(2), system(3), utime(2), wait3(2), wait4(2),
wait(2), waitpid(2),
* More internationalization support has been added.
* A bug has been fixed in the C++ insulation.
Version 0.2 (2008-Nov-11)
* Coverage now includes chmod(2), chown(2), dup(2), fchdir(2),
fchmod(2), fstat(2), ftruncate(2), fwrite(3), mkdir(2), readdir(3),
readlink(2), remove(3), rmdir(2) and truncate(2).
* The lsof(1) command is used to obtain supplementary file information
on those systems with limited /proc implementations.
* The explanations now understand Linux capabilities.
Version 0.1 (2008-Oct-26)
First public release.
Reference Manual libexplain Read Me(libexplain)