printf does not always display warning messages on write errors

[Stefano Lattarini]

Hi everybody.

I found the following bug while running some of my bash scripts on 
GNU/Linux with stdout redirected to /dev/full, to see if write errors
where correctly detected and reported.

It turned out that, on write errors, the printf builtin correctly
returns a non-zero status (thus my scripts at least had a correct
exit status), but unfortunately it does not always display a suitable
error message on stderr; in particular, it fails to do so if the
printed  string does *not* end with a newline. On the contrary, the
echo builtin both returns a non-zero status and write a clear error
message on standard error, even if called with the `-n' option (so
that the printed string does not end with a newline).

Examples (tested with both bash 3.2 and bash 4.0, more details about 
versions and system information will follow):

  $ ls -l /dev/full
  crw-rw-rw- 1 root root 1, 7 Sep  2 18:36 /dev/full
  
  $ cat printf-bug.sh
  echo "* `type printf`"
  echo "* `type echo`"
  # - - -
  printf x >/dev/full
    echo a:$?
  printf "%s\n" x >/dev/full
    echo b:$?
  echo -n x >/dev/full
    echo c:$?
  echo x >/dev/full
    echo d:$?
  # - - -
  exit 0
  
  $ bash printf-bug.sh # using either bash 4.0 or 3.2
  * printf is a shell builtin
  * echo is a shell builtin
  a:1
  printf-bug.sh: line 6: printf: write error: No space left on device
  b:1
  printf-bug.sh: line 8: echo: write error: No space left on device
  c:1
  printf-bug.sh: line 10: echo: write error: No space left on device
  d:1

By the way, bash 3.0 behaves far worser (I don't known if you can
found this info useful, but anyway here it is):

  $ bash-3.0 printf-bug.sh
  * printf is a shell builtin
  * echo is a shell builtin
  a:0
  b:0
  c:1
  d:1

Here are the details on my system and the bash shells used.

 ---

Details on operating system:

 $ uname -s -r -m -o
 Linux  2.6.26-1-686  i686  GNU/Linux
 $ lsb_release -i -d -r -c
 Distributor ID: Debian
 Description:  Debian GNU/Linux testing/unstable
 Release:  testing/unstable
 Codename:  n/a
 $ cat /etc/debian_version
 squeeze/sid

 ---

Details on bash versions:

Bash 4.0
---------------
 Installed from debian package "bash", version "4.0-4"
 Complete version string:  4.0.28(1)-release
 
Information from bashbug [Automatically generated]:
  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 -Wall
  Machine Type: i486-pc-linux-gnu

Bash Version: 4.0
Patch Level: 28
Release Status: release

Bash 3.2
---------------
 Installed by hand from official tarball.
 Complete version string: 3.2.0(1)-release

Information from bashbug [Automatically generated]:
  Machine: i686
  OS: linux-gnu
  Compiler: gcc
  Compilation CFLAGS:
    -DPROGRAM='bash'
    -DCONF_HOSTTYPE='i686'
    -DCONF_OSTYPE='linux-gnu'
    -DCONF_MACHTYPE='i686-pc-linux-gnu'
    -DCONF_VENDOR='pc'
    -DLOCALEDIR='/opt/vintage/bash-3.2/share/locale'
    -DPACKAGE='bash'
    -DSHELL
    -DHAVE_CONFIG_H
    -I. -I. -I./include -I./lib
    -g -O2
  Machine Type: i686-pc-linux-gnu

Bash Version: 3.2
Patch Level: 0
Release Status: release

Bash 3.0
---------------
 Installed by hand from official tarball.
 Complete version string: 3.00.0(1)-release

Information from bashbug [Automatically generated]:
  Machine: i686
  OS: linux-gnu
  Compiler: gcc
  Compilation CFLAGS:
    -DPROGRAM='bash'
    -DCONF_HOSTTYPE='i686'
    -DCONF_OSTYPE='linux-gnu'
    -DCONF_MACHTYPE='i686-pc-linux-gnu'
    -DCONF_VENDOR='pc'
    -DLOCALEDIR='/opt/vintage/bash-3.0/share/locale'
    -DPACKAGE='bash'
    -DSHELL
    -DHAVE_CONFIG_H
    -I. -I. -I./include -I./lib
    -g -O2
  Machine Type: i686-pc-linux-gnu

Bash Version: 3.0
Patch Level: 0
Release Status: release

 ---

Regards,
   Stefano