Kir Kolyshkin made a start, but I think much more needs to
be said...
Reviewed-by: Serge E. Hallyn <serge@hallyn.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
From an email conversation with Alexis:
Hello Alexis,
On 8/6/21 7:06 PM, Alexis Wilke wrote:
> Hi guys,
>
> The pthread_setname_np(3) manual page has an example where the second
> argument is used to get a size of the thread name.
>
> https://man7.org/linux/man-pages/man3/pthread_setname_np.3.html#EXAMPLES
>
> The current code:
>
> rc = pthread_getname_np(thread, thread_name,
> (argc > 2) ? atoi(argv[1]) : NAMELEN);
>
> The suggested code:
>
> rc = pthread_getname_np(thread, thread_name,
> (argc > 2) ? atoi(argv[2]) : NAMELEN);
I agree that there's a problem, but I think we could go even simpler:
rc = pthread_getname_np(thread, thread_name, NAMELEN);
> I'm thinking that maybe the author meant to compute the length like so:
>
> rc = pthread_getname_np(thread, thread_name,
> (argc > 2) ? strlen(argv[1]) + 1 :
> NAMELEN);
>
> But I think that the atoi() points to using argv[2] as a number
> representing the length.
>
> (Of course, it should be tested against NAMELEN as a maximum, but I
> understand that examples do not always show how to verify each possible
> error).
I imagine that the author's intention was to allow the user to do
experiments where argv[2] specified a number less than NAMELEN,
in order to see the resulting ERANGE error. But, that experiment
is of limited value, and complicates the code unnecessarily, IMO,
so that's why I made the change above.
--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
Reported-by: Alexis Wilke <alexis@m2osw.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Phrases such as "In the new mount API" will date fast. Remove it.
Also:
* Make it clear that MOUNT_ATTR__ATIME expresses a bit field.
* Replace 'enum' with 'enumeration'.
* Clarify what is meant by "partially" set MOUNT_ATTR__ATIME.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
These types are already well described in mount_namespaces(7);
indeed, much of the text from that page seems to have just been
cut and pasted into this page! Simply referring the reader to
mount_namespaces(7) is sufficient.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Point out that this field can have the value zero, meaning
no change. And avoid discussions of 'enum', and simply say
that otherwise the field has one of the MS_* values.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Reported-by: Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Having this discussion under DESCRIPTION clutters that section,
and has the effect of burying the discussion of propagation. Move
the discussion to NOTES, to make the page more readable.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
- Change some instances of "-" to "\"
- Use C99 style (declare variables nearer use in code)
- Add a bit of white space
- Remove one 'const...const' added by Alex that caused
compiler warnings
- Use "reverse Christmas tree" form for declarations in main()
- Other minor changes
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
We don't really need ext4(5) and xfs(5) here. They provide
no further info that is directly relevant to the reader of
mount_setattr(2).
clone3(2) isn't necessary because it is the same page as clone(2).
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
- Fix SYNOPSIS to fit in 78 columns
Also, we don't show when an include is included for a specific type,
unless that header is included _only_ for the type,
or there might be confusion (e.g., termios).
Instead, that type should be documented in system_data_types(7),
with a link page mount_attr-struct(3).
- Fix references to mount_setattr(). See man-pages(7):
Any reference to the subject of the current manual page should be writ‐
ten with the name in bold followed by a pair of parentheses in Roman
(normal) font. For example, in the fcntl(2) man page, references to
the subject of the page would be written as: fcntl(). The preferred
way to write this in the source file is:
.BR fcntl ()
- Fix line breaks according to semantic newline rules (and add some commas)
- Fix wrong usage of .IR when .RI should have been used
- Fix formatting of variable part in FOO<number>:
- Make italic the variable part (as groff_man(7) recommends)
- Remove <>
- Use syntax recommended by G. Branden Robinson (groff)
- Fix unnecessary uses of .BR or .IR when .B or .I would suffice
- Fix formatting of punctuation
In some cases, it was in italics or bold, and it should always be in roman.
- Use uppercase to begin text, even in bullet points, since those were
multi-sentence.
- Simplify usage of .RS/.RE in combination with .IP
- s/fat/FAT/ as fs(7) does
- Slightly reword some sentences for consistency
- Use Linux-specific for consistency with other pages (in VERSIONS)
- EXAMPLES: Place the return type in a line of its own (as in other pages)
- Fix alignment of code
- Replace unnecessary use of the GNU extension ({}) by do {} while (0)
In that case, there was no return value (moreover, it's a noreturn).
- Break complex declaration lines into a line for each variable
The variables were being initialized, some to non-zero values,
so for clarity, a line for each one seems more appropriate.
- Add const to pointers when possible
- s/\\/\e/
- Remove unmatched groff commands
Cc: Christian Brauner <brauner@kernel.org>
Signed-off-by: Alejandro Colomar <alx.manpages@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Note the use of FUTEX_CLOCK_REALTIME for selecting the clock,
and eliminate repetition of details already covered in the
description of FUTEX_LOCK_PI.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
FUTEX_LOCK_PI2 is a new futex operation which was recently introduced into the
Linux kernel. It works exactly like FUTEX_LOCK_PI. However, it has support for
selectable clocks for timeouts. By default CLOCK_MONOTONIC is used. If
FUTEX_CLOCK_REALTIME is specified then the timeout is measured against
CLOCK_REALTIME.
This new operation addresses an inconsistency in the futex interface:
FUTEX_LOCK_PI only works with timeouts based on CLOCK_REALTIME in contrast to
all the other PI operations.
Document the FUTEX_LOCK_PI2 command.
Signed-off-by: Kurt Kanzenbach <kurt@linutronix.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Alejandro Colomar <alx.manpages@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
- Move example program to a new EXAMPLES section
- Invert logic in the handler to have the failure in the
conditional path, and the success out of any conditionals.
- Use NULL, EXIT_SUCCESS, and EXIT_FAILURE instead of magic numbers
- Separate declarations from code
- Put function return type on its own line
- Put function opening brace on its line
Cc: Peter Collingbourne <pcc@google.com>
Signed-off-by: Alejandro Colomar <alx.manpages@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
See https://bugzilla.kernel.org/show_bug.cgi?id=212385
some/path/dir/ is not always the same as some/path/dir/:
$ mkdir u
$ rmdir u/.
rmdir: failed to remove 'u/.': Invalid argument
$ rmdir u
$
The text in POSIX.1-2018 Section 4.13 ("Pathname Resolution")
is helpful in pointing to a better wording.
Reported-by: Askar Safin <safinaskar@mail.ru>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Emanuele Torre via linux-man@:
[
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:
$ ldd /bin/ls | sed 's/^ */ /'
linux-vdso.so.1 (0x00007ffcc3563000)
libselinux.so.1 => /lib64/libselinux.so.1 (0x00007f87e5459000)
libcap.so.2 => /lib64/libcap.so.2 (0x00007f87e5254000)
libc.so.6 => /lib64/libc.so.6 (0x00007f87e4e92000)
libpcre.so.1 => /lib64/libpcre.so.1 (0x00007f87e4c22000)
libdl.so.2 => /lib64/libdl.so.2 (0x00007f87e4a1e000)
/lib64/ld-linux-x86-64.so.2 (0x00005574bf12e000)
libattr.so.1 => /lib64/libattr.so.1 (0x00007f87e4817000)
libpthread.so.0 => /lib64/libpthread.so.0 (0x00007f87e45fa000)
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:
$ ldd /bin/ls | xxd | head -1
00000000: 096c 696e 7578 2d76 6473 6f2e 736f 2e31 .linux-vdso.so.1
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.
Those, on my system, are:
* /usr/lib/ld-linux.so.2
* /usr/lib64/ld-linux-x86-64.so.2
* /usr/libx32/ld-linux-x32.so.2
And they all seem to also be part of glibc.
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.
Cheers.
emanuele6
[1]: https://man7.org/linux/man-pages/man1/ldd.1.html
[2]: https://sourceware.org/git/?p=glibc.git;a=blob;f=elf/ldd.bash.in;h=ba736464ac5e4a9390b1b6a39595035238250232;hb=5188a9d0265cc6f7235a8af1d31ab02e4a24853d
[3]: https://sourceware.org/git/?p=glibc.git;a=commit;h=6a76c115150318eae5d02eca76f2fc03be7bd029
///////
$ 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.
]
Reported-by: EmanueleTorre <torreemanuele6@gmail.com>
Signed-off-by: Alejandro Colomar <alx.manpages@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
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>
Michael Kerrisk