[
I was reading the man page for ldd(1)[1]; and I read this in the first
paragraph of the DECRIPTION section:
ldd prints the shared objects (shared libraries) required by each
program or shared object specified on the command line. An
example of its use and output (using sed(1) to trim leading white
space for readability in this page) is the following:
This is a little confusing though since that sed(1) command does not
seem to work. (and also potentially misleading for someone who is trying
figure out how to parse ldd(1)'s output.)
ldd(1) prepends a TAB character (0x09) to each line, not spaces:
I read ldd(1)'s source code[2] (it is part of glibc) and it seems to be
a bash script that tries to use different rtld programs ( ld.so(8) )
from an RTLDLIST.
I have tried to follow the git history of glibc to see when the switch
from spaces to the TAB character occured, but, to me, it seems like
glibc.git/elf/rtld.c has always used '\t'; at since 6a76c115150318eae5d02eca76f2fc03be7bd029[3] (358th commit since glibc
started using the git repository repository - Nov 18th 1995): before
that commit there are not any results for `git grep '\\t'` in the elf
directory and I did not investigate further.
Still, at the time of that commit, glibc did not seem to have an ldd(1)
utility.
Perhaps the man page is old and its original author was using and
documenting an ldd(1) utility that was not part of glibc when he was
writing it.
Anyhow, since I think that sed(1) command will not work on any system
that uses, at least, the most recent version of glibc (because lld(1)
and the ld.so(8) programs it depends on are all part of glibc), I think
that that example should be changed to avoid confusions.
The output format of ldd(1) does not seem to be clearly defined, so I
think this would be a good option:
$ ldd /bin/ls | sed 's/^[[:space:]]*/ /'
NB: ^\s* should also work on most GNU/Linux systems, but \s is
non-standard or documented so I don not suggest using it in the man
page.
Another option could be to remove "the pipe to sed(1)" part and the note
in parentheses that explains why it was used by the original author.
$ uname -a
Linux t420 5.10.54-1-lts #1 SMP Wed, 28 Jul 2021 15:05:20 +0000
x86_64 GNU/Linux
$ pacman -Qo ldd
/usr/bin/ldd is owned by glibc 2.33-5
$ pacman -Qo /usr/share/man/man1/ldd.1.gz
/usr/share/man/man1/ldd.1.gz is owned by man-pages 5.12-2
$ pacman -Qo /usr/lib/ld-linux.so.2
/usr/lib/ld-linux.so.2 is owned by lib32-glibc 2.33-5
$ pacman -Qo /usr/lib64/ld-linux-x86-64.so.2
/usr/lib/ld-linux-x86-64.so.2 is owned by glibc 2.33-5
$ pacman -F /usr/libx32/ld-linux-x32.so.2 || echo not available on arch linux.
not available on arch linux.
]
Cc: James O. D. Hunt <jamesodhunt@gmail.com> Signed-off-by: Alejandro Colomar <alx.manpages@gmail.com> Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Explain that `optstring` cannot contain a semi-colon (`;`)
character.
[mtk: verified with a small test program; see also posix/getopt.c
in the glibc sources:
if (temp == NULL || c == ':' || c == ';')
{
if (print_errors)
fprintf (stderr, _("%s: invalid option -- '%c'\n"), argv[0], c);
d->optopt = c;
return '?';
}
]
Also explain that `optstring` can include `+` as an option
character, possibly in addition to that character being used as
the first character in `optstring` to denote `POSIXLY_CORRECT`
behaviour.
[mtk: verified with a small test program.]
switch (opt) {
case 'p': pstr = optarg; break;
case 'x': xfnd++; break;
case ';': printf("Got semicolon\n"); break;
case '+': printf("Got plus\n"); break;
case ':': usageError(argv[0], "Missing argument", optopt);
case '?': usageError(argv[0], "Unrecognized option", optopt);
default:
printf("Unexpected case in switch()\n");
exit(EXIT_FAILURE);
}
}
if (xfnd != 0)
printf("-x was specified (count=%d)\n", xfnd);
if (pstr != NULL)
printf("-p was specified with the value \"%s\"\n", pstr);
if (optind < argc)
printf("First nonoption argument is \"%s\" at argv[%d]\n",
argv[optind], optind);
exit(EXIT_SUCCESS);
}
Michael Kerrisk [Sun, 8 Aug 2021 09:24:16 +0000 (11:24 +0200)]
readv.2, pipe.7: Make text on pipe writes more general to avoid a confusion in writev(2)
After a patch proposal from наб triggered by concerns that, when
talking about PIPE_BUF, pipe(7) explicitly mentions write(2) but
not writev(2), I've concluded that the reference in writev(2) to
pipe(7) is not needed (mea culpa; I added that text), and I think
the text in pipe(7) could be written to be closer to the POSIX
spec, which doesn't talk about "write() calls", but simply about
"writes".
Reported-by: наб <nabijaczleweli@nabijaczleweli.xyz> Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Michael Kerrisk [Sun, 8 Aug 2021 02:34:37 +0000 (04:34 +0200)]
readv.2: Minor fixes (part 2) to Will Manley's patch
Mainly: I generally don't want us to be including URLs to mailing
list discussions in a manual page. Either, the issue in the
discussion is worth writing up in the manual page (so that
the reader doesn't have to look elsewhere), or the details
are less important, in which case it is sufficient to note the
existence of the bug. I think this is an example of the latter.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Will Manley [Wed, 28 Jul 2021 20:19:37 +0000 (22:19 +0200)]
readv2: Note preadv2(..., RWF_NOWAIT) bug in BUGS section
To save the next person before they fall foul of it. See
<https://lore.kernel.org/linux-fsdevel/fea8b16d-5a69-40f9-b123-e84dcd6e8f2e@www.fastmail.com/T/#u>
and <https://github.com/tokio-rs/tokio/issues/3803> for more information.
Signed-off-by: Will Manley <will@williammanley.net> Signed-off-by: Alejandro Colomar <alx.manpages@gmail.com> Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
This flag was recently added to Linux 5.14 by a patch I wrote:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=0ae71c7720e3ae3aabd2e8a072d27f7bd173d25c
This patch adds documentation for the flag, the error code that the flag
added and explains in the caveat when it is useful.
Dan Robertson [Wed, 28 Jul 2021 20:19:42 +0000 (22:19 +0200)]
man2/fallocate.2: tfix documentation of shared blocks
Fix a typo in the documentation of using fallocate to allocate shared
blocks. The flag FALLOC_FL_UNSHARE should instead be documented as
FALLOC_FL_UNSHARE_RANGE.
Fixes: 63a599c657d8 ("man2/fallocate.2: Document behavior with shared blocks") Signed-off-by: Dan Robertson <dan@dlrobertson.com> Reviewed-by: Darrick J. Wong <djwong@kernel.org> Signed-off-by: Alejandro Colomar <alx.manpages@gmail.com> Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
posixoptions.7: Fix legacy functions list (s/getcwd/getwd/)
Alan:
[
The on-line copy of the manual page "posixoptions(7)" dated
2018-04-30 has an entry for "getcwd()" in the section headed
"XSI - _XOPEN_LEGACY - _SC_XOPEN_LEGACY".
I believe that entry should be "getwd()" as that is the API call
which was present in X/Open-6 but withdrawn in X/Open-7.
]
mtk: confirmed by reviewing the table ("Removed Functions and
Symbols in Issue 7") at the end of Section B.1.1 on page
3564 of IEEE Std 1003.1, 2016 Edition.
Reported-by: Alan Peakall <Alan.Peakall@helpsystems.com> Signed-off-by: Alejandro Colomar <alx.manpages@gmail.com> Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Michael Kerrisk [Sun, 8 Aug 2021 00:13:49 +0000 (02:13 +0200)]
vdso.7: Update CLOCK_REALTIME_COARSE and CLOCK_MONOTONIC_COARSE info for powerpc
See https://bugzilla.kernel.org/show_bug.cgi?id=213419
ppc/32 and ppc/64 sections both have the following note:
The CLOCK_REALTIME_COARSE and CLOCK_MONOTONIC_COARSE clocks are
not supported by the __kernel_clock_getres and
__kernel_clock_gettime interfaces; the kernel falls back to the
real system call
This note has been wrong from quite some time now, since commit 654abc69ef2e ("powerpc/vdso32: Add support for
CLOCK_{REALTIME/MONOTONIC}_COARSE") and commit 5c929885f1bb ("powerpc/vdso64: Add support for
CLOCK_{REALTIME/MONOTONIC}_COARSE")
Reported-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
ascii.7: ffix: add vertical rule to separate the two columns
I regularly get mildly lost in this table (and, indeed, didn't realise
it had two columns the first few times I used it to look at something
from the left column) ‒ separating the two columns improves clarity,
and makes which soup of numbers belongs to which character
much more obvious
Other encodings don't need this as they don't use double-columnated
tables
Kir Kolyshkin [Wed, 28 Jul 2021 20:19:49 +0000 (22:19 +0200)]
user_namespaces.7: Fix a reference to a kernel document
The file being referred to no longer exists, as it was moved to
*.rst first (commit 20a78ae9ed297f2) and then to under
admin-guide (commit bf6b7a742e3f82b). Both those commits
are from 2019 (Linux 5.3).
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com> Signed-off-by: Alejandro Colomar <alx.manpages@gmail.com> Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
наб [Sat, 12 Jun 2021 08:27:39 +0000 (10:27 +0200)]
getline.3: !*lineptr is sufficient
No implementation or spec requires *n to be 0 to allocate a new buffer:
* musl checks for !*lineptr
(and sets *n=0 for later allocations)
* glibc checks for !*lineptr || !*n
(but only because it allocates early)
* NetBSD checks for !*lineptr
(and sets *n=0 for later allocations)
(but specifies *n => mlen(*lineptr) >= *n as a precondition,
to which this appears to be an exception)
* FreeBSD checks for !*lineptr and sets *n=0
(and specifies !*lineptr as sufficient)
* Lastly, POSIX.1-2017 specifies:
> If *n is non-zero, the application shall ensure that *lineptr
> either points to an object of size at least *n bytes,
> or is a null pointer.
The new wording matches POSIX, even if it arrives at the point slightly
differently
projects / thirdparty / man-pages.git / log
