Re: doesn't bash do variable subst. or quote removal on function statement

[Andreas Schwab]

Linda Walsh  writes:

>>  shopt -s expand_aliases; alias my=declare
>>  declare fn=myfunc## function name in variable 
> doesn't work
>>  function $fn { echo $fn ; }
> -bash: `$fn': not a valid identifier
>>my -pf myfunc
> -bash: declare: myfunc: not found
>>
>>  def="function $fn () { echo $fn ; }"  ## but same statement, eval'd works

That's not the same statement.  The same statement would be

def='function $fn () { echo $fn ; }'

Andreas.

-- 
Andreas Schwab, sch...@linux-m68k.org
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."

implicit redirection of background within pipeline

[Martin D Kealey]

Configuration Information [Automatically generated, do not change]:
Machine: x86_64
OS: linux-gnu
Compiler: gcc
Compilation CFLAGS:  -DPROGRAM='bash' -DCONF_HOSTTYPE='x86_64'
-DCONF_OSTYPE='linux-gnu' -DCONF_MACHTYPE='x86_64-pc-linux-gnu'
-DCONF_VENDOR='pc' -DLOCALEDIR='/usr/share/locale' -DPACKAGE='bash' -DSHELL
-DHAVE_CONFIG_H   -I.  -I../. -I.././include -I.././lib  -D_FORTIFY_SOURCE=2
-g -O2 -fstack-protector --param=ssp-buffer-size=4 -Wformat
-Werror=format-security -Wall
uname output: Linux treehug.home.kurahaupo.gen.nz 3.13.0-55-generic
#94-Ubuntu SMP Thu Jun 18 00:27:10 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux
Machine Type: x86_64-pc-linux-gnu

Bash Version: 4.3
Patch Level: 11
Release Status: release

Description:
The first backgrounded element within a pipeline component has its
stdin redirected to /dev/null; this does not apply to the second and
subsequent background elements.

On a Linux system this can be observed with:
echo x | ( ls -ld /proc/self/fd/0 &
   ls -ld /proc/self/fd/0 &
   wait )

On other systems it is apparent simply with:
echo x | ( cat & wait )
# no output is produced

Repeat-By:
# this command produces no output:
echo x | ( cat & wait )

Fix:
# this is only a work-around:
echo x ( :& cat & wait )

"read < <(:); echo $?" prints 0 when job control is disabled (should be 1?)

[Alastair Hughes]

When job control is enabled:
  $ read < <(:); echo $?
  1
When job control is disabled:
  $ read < <(:); echo $?
  0

Is this a bug, or valid behavior? It seems to be caused by 
already_making_children being set in the bash without job control; the shell 
waits for a child and sets exec_status to 0 (the read builtin returns 1). I've 
reproduced this on both an x86_64 machine and in a MIPS VM, with both bash 
4.3.42, and bash 4.4.0 (ie devel).

Note that (with job control disabled)
  $ : | read; echo $?
  1
and
  $ false < <(:); echo $?
  0
or,
  $ false <(:); echo $?
  0
while
  $ false; echo $?
  1
(using a process substitution seems to trigger the behavior)

Alastair Hughes

Re: implicit redirection of background within pipeline

[Piotr Grzybowski]

hey,

 I am quite sure it happens here (devel branch, at
6f82653c5ef09aeeeba4376a1c65ce86c3605c00):

execute_cmd.c +5115:
   if ((cmdflags & CMD_STDIN_REDIR) &&
  pipe_in == NO_PIPE &&
  (stdin_redirects (redirects) == 0))
 async_redirect_stdin ();

 but after reading the comments some 3.5k lines earlier I am not sure
how to fix it; of course commenting out the if in
execute_cmd.c:5112-5115 solves it, but who can tell what it breaks?

cheers,
pg



On Sun, Jan 10, 2016 at 8:23 AM, Martin D Kealey
 wrote:
>
> Configuration Information [Automatically generated, do not change]:
> Machine: x86_64
> OS: linux-gnu
> Compiler: gcc
> Compilation CFLAGS:  -DPROGRAM='bash' -DCONF_HOSTTYPE='x86_64'
> -DCONF_OSTYPE='linux-gnu' -DCONF_MACHTYPE='x86_64-pc-linux-gnu'
> -DCONF_VENDOR='pc' -DLOCALEDIR='/usr/share/locale' -DPACKAGE='bash' -DSHELL
> -DHAVE_CONFIG_H   -I.  -I../. -I.././include -I.././lib  -D_FORTIFY_SOURCE=2
> -g -O2 -fstack-protector --param=ssp-buffer-size=4 -Wformat
> -Werror=format-security -Wall
> uname output: Linux treehug.home.kurahaupo.gen.nz 3.13.0-55-generic
> #94-Ubuntu SMP Thu Jun 18 00:27:10 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux
> Machine Type: x86_64-pc-linux-gnu
>
> Bash Version: 4.3
> Patch Level: 11
> Release Status: release
>
> Description:
> The first backgrounded element within a pipeline component has its
> stdin redirected to /dev/null; this does not apply to the second and
> subsequent background elements.
>
> On a Linux system this can be observed with:
> echo x | ( ls -ld /proc/self/fd/0 &
>ls -ld /proc/self/fd/0 &
>wait )
>
> On other systems it is apparent simply with:
> echo x | ( cat & wait )
> # no output is produced
>
> Repeat-By:
> # this command produces no output:
> echo x | ( cat & wait )
>
> Fix:
> # this is only a work-around:
> echo x ( :& cat & wait )
>
>