Configuration Information [Automatically generated, do not change]:
Machine: i486
OS: linux-gnu
Compiler: gcc
Compilation CFLAGS: -DPROGRAM='bash' -DCONF_HOSTTYPE='i486'
-DCONF_OSTYPE='linux-gnu' -DCONF_MACHTYPE='i486-pc-linux-gnu'
-DCONF_VENDOR='pc' -DLOCALEDIR='/usr/share/locale' -DPACKAGE='bash'
-DSHELL -DHAVE_CONFIG_H -I. -I../bash -I../bash/include
-I../bash/lib -g -O2
uname output: Linux akula 2.6.17.7 #4 Sat Sep 8 23:10:46 CEST 2007 i686
GNU/Linux
Machine Type: i486-pc-linux-gnu
Bash Version: 3.1
Patch Level: 17
Release Status: release
Description:
With Unix-98 ptys, the builtin echo command gets executed
even when writing to stdout or redirecting to stderr fails, and
the output gets written to the wrong file descriptor if any other
redirection is used in the script.
Repeat-By:
For example, with the following script:
while [ 1 ];do
echo Test1
echo Test2 >> file.txt
sleep 1
done
As expected, when this script is run in the background (&), the
console
slowly fills with "Test1" lines, and the file.txt file slowly
fills with
"Test2" lines.
Now exit the shell leaving the script running (don't simply
close the
xterm, that'd kill the script. Type "exit"). Since the terminal has
closed, stdout is closed, so "echo Test1" should fail. It doesn't,
instead it writes "Test1" lines into whatever open file
descriptor it
can find. In this case, file.txt starts filling up with
Test2
Test1
Test2
Test1
...
This does not happen with BSD-style ptys, because apparently
when the
terminal is closed, the tty seen by the detached bash script stays
intact, and whatever is written to the now-closed terminal is simply
discarded by the kernel, so the script keeps seeing open stdout and
stderr file descriptors. In the case of Unix-98 ptys, this bug
happens
because the tty file descriptors the bash script uses are really
closed
This also does not happen with an external echo command: with
/bin/echo,
the redirection fails and the command is not executed, as expected.
