Hi Emanuele and Alex, On 8/8/21 10:41 AM, Alejandro Colomar wrote: > 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@xxxxxxxxx> > Signed-off-by: Alejandro Colomar <alx.manpages@xxxxxxxxx> Emanuele, thanks for all of the details. Alex, thanks for the patch. Applied. Cheers, Michael > --- > man1/ldd.1 | 5 +---- > 1 file changed, 1 insertion(+), 4 deletions(-) > > diff --git a/man1/ldd.1 b/man1/ldd.1 > index ed1ab3c05..8bb1410d5 100644 > --- a/man1/ldd.1 > +++ b/man1/ldd.1 > @@ -23,14 +23,11 @@ ldd \- print shared object dependencies > 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 > -.BR sed (1) > -to trim leading white space for readability in this page) > is the following: > .PP > .in +4n > .EX > -$ \fBldd /bin/ls | sed \(aqs/^ */ /\(aq\fP > +$ \fBldd /bin/ls\fP > linux\-vdso.so.1 (0x00007ffcc3563000) > libselinux.so.1 => /lib64/libselinux.so.1 (0x00007f87e5459000) > libcap.so.2 => /lib64/libcap.so.2 (0x00007f87e5254000) > -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/
