0000973: msh grave substitution does not work if stdin/stdout are not already open

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Category

Severity

Reproducibility

Date Submitted

Last Update

0000973

[BusyBox] Other

minor

always

07-27-06 06:12

02-14-08 09:14

Reporter

Keith Young

View Status

public

Assigned To

BusyBox

Priority

normal

Resolution

fixed

Status

closed

Product Version

1.01

Summary

0000973: msh grave substitution does not work if stdin/stdout are not already open

Description

I tried using busybox sh as the script processor /sbin/hotplug (Linux 2.6.16)
Substitutions such as:
d=`date`
return empty.

Additional Information

Using strace I could see what was happening. The hotplug executable is invoked
from the kernel (somehow) and has no stdin/stdout attached. Consequently when
the pipe is created for communication with the sub-shell it has fd's [0,1].
After the vfork() (see msh.c, grave()) the child process does:

    dup2(pf[1], 1);
    closepipe(pf);

Fd 1 gets successfully duplicated to 1 and then closed. Hence no more output is possible on stdout from the sub-shell.

A fix that works for me is:

    if (pf[1] != 1)
    {
        dup2(pf[1], 1);
        closepipe(pf);
    }
    else
        close(pf[0]);

Attached Files

Relationships

Notes
(0004744) vda 02-14-08 09:14	Fixed sometime ago in svn: xmove_fd(pf[1], 1); if (pf[0] != 1) close(pf[0]);

Issue History
Date Modified	Username	Field	Change
07-27-06 06:12	Keith Young	New Issue
07-27-06 06:12	Keith Young	Status	new => assigned
07-27-06 06:12	Keith Young	Assigned To	=> BusyBox
02-14-08 09:14	vda	Status	assigned => closed
02-14-08 09:14	vda	Note Added: 0004744
02-14-08 09:14	vda	Resolution	open => fixed