On Thu, 25 Nov 2010, Jonathan Nieder wrote:
> severity 604993 normal
> quit
>
> Hi Tim,
>
> Tim Connors wrote:
>
> > When /bin/sh is linked to dash, if <prog> is a shell script (/bin/sh
> > or /bin/bash), that shell script sees $PPID as being the "sh -c" process.
>
> Could you give an example? I tried:
>
> $ sh -c 'echo $PPID; echo $$'
> 18562
> 18564
> $ python -c 'import os; os.system("echo $PPID; echo $$");'
> 18577
> 18578
>
> so I suspect I am missing something.
75427,45> ps $$
PID TTY STAT TIME COMMAND
2520 pts/29 Ss 0:01 bash
75428,46> /bin/bash -c "bash -c \"echo \\\$PPID ; ps \\\$PPID\""
2520
PID TTY STAT TIME COMMAND
2520 pts/29 Ss 0:01 bash
75429,47> /bin/dash -c "bash -c \"echo \\\$PPID ; ps \\\$PPID\""
5542
PID TTY STAT TIME COMMAND
5542 pts/29 S+ 0:00 /bin/dash -c bash -c "echo \$PPID ; ps \$PPID"
(the first /bin/bash or /bin/dash mimics /bin/sh being called with those
set as links, the second /bin/bash mimicks the #!/bin/bash line of a
script being called by system() (equivalentl results with #!/bin/sh or
#!/bin/dash), or indeed any process that reads the PPid line from
/proc/.../status.
> > I have marked this as "grave", because it breaks unrelated parts of
> > the system
>
> No.
I strongly disagree.
It causes the PPid line in /proc/$pid/status to be WRONG for any program
or script if it was executed by the system() routine provided in libc, if
and only if dash is installed as /bin/sh.
--
TimC
If you ever fear that machines will surpass humans in intelligence,
just ask Microsoft to write the OS. -- POTU in RHOD
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