On Wed, 3 Jan 2001, Mevorach, Assaf wrote:
> hey even for the sake of the argument you cant pretend you dont know that
> libc DOESNT use dynamic load library (dlopen).
why do you think that? libc contains code that uses /etc/nsswitch.conf to
check where to get certain types of info from (files, nis, nisplus...) and
it then dynamically loads a library that has functions to access those
files. how you could see that? 'ldd' a file on your system, such as
'/usr/bin/top'. here is the output on this redhat 6.2 system:
[choo@simey ~]$ ldd /usr/bin/top
libproc.so.2.0.6 => /lib/libproc.so.2.0.6 (0x4001a000)
libncurses.so.4 => /usr/lib/libncurses.so.4 (0x40026000)
libc.so.6 => /lib/libc.so.6 (0x40068000)
/lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
then run 'top', check its PID, and run '/usr/sbin/lsof -p <PID>'.
here is the output on this machine:
[choo@simey ~]$ /usr/sbin/lsof -p 863
COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME
top 863 choo cwd DIR 3,67 6144 51150 /prog/choo
top 863 choo rtd DIR 3,2 1024 2 /
top 863 choo txt REG 3,3 34896 34672 /usr/bin/top
top 863 choo mem REG 3,2 340663 13952 /lib/ld-2.1.3.so
top 863 choo mem REG 3,2 44108 14056 /lib/libproc.so.2.0.6
top 863 choo mem REG 3,3 262884 12216
/usr/lib/libncurses.so.4.0
top 863 choo mem REG 3,2 4101324 13959 /lib/libc-2.1.3.so
top 863 choo mem REG 3,2 246652 13990
/lib/libnss_files-2.1.3.so
top 863 choo 0u CHR 4,4 7479 /dev/tty4
top 863 choo 1u CHR 4,4 7479 /dev/tty4
top 863 choo 2u CHR 4,4 7479 /dev/tty4
top 863 choo 3r REG 0,1 0 3 /proc/uptime
top 863 choo 4r REG 0,1 0 17 /proc/stat
top 863 choo 5r REG 0,1 0 2 /proc/loadavg
top 863 choo 6r REG 0,1 0 4 /proc/meminfo
as you can see, libnss_files-2.1.3 was magically opened by 'top', and this
is not something that 'top' does on its own - its part of libc's services.
> BTW,where/Why did you gather all this knowledge about Linux/Unix
> executable and linkable format ?
why? because i needed some of it, and was curious about the rest. how?
reading, playing and experimenting with processes. some of it is due to
work. some of it - from people such as you.
--
guy
"For world domination - press 1,
or dial 0, and please hold, for the creator." -- nob o. dy
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