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digitalmars.D.learn - 2.068.0 std.process.executeShell how to set the shell?

reply "albatroz" <rmcjustino gmail.com> writes:
Hi, since the upgrade to the latest version the function 
executeShell (also the other functions), is not working has it 
used to be, older versions of the compiler did not require any 
change or setting the SHELL.

How to change the SHELL, that is used by executeShell? userShell 
will always return /bin/sh.

I've tested by setting the SHELL to /bin/bash using the 
environment function. If I execute echo $SHELL inside the 
executeShell it will show /bin/bash has expected.

My issue is that the command I'm executing inside executeShell is 
throwing and error and showing that the execution is done by 
/bin/sh.

My code:
executeShell("diff -u <(echo "~data1~") <(echo "~data2~")");

Output:
/bin/sh: 1: Syntax error: "(" unexpected

This is caused by a limitation from /bin/sh that cannot perform 
process substitution.

Can this commit be the reason? 
https://github.com/D-Programming-Language/phobos/commit/a524a3571b18e440c4dd751fcf4e2d00b834fb22
Sep 01 2015
parent reply Jonathan M Davis via Digitalmars-d-learn writes:
On Tuesday, September 01, 2015 21:55:28 albatroz via Digitalmars-d-learn wrote:

 Hi, since the upgrade to the latest version the function
 executeShell (also the other functions), is not working has it
 used to be, older versions of the compiler did not require any
 change or setting the SHELL.

 How to change the SHELL, that is used by executeShell? userShell
 will always return /bin/sh.

 I've tested by setting the SHELL to /bin/bash using the
 environment function. If I execute echo $SHELL inside the
 executeShell it will show /bin/bash has expected.

 My issue is that the command I'm executing inside executeShell is
 throwing and error and showing that the execution is done by
 /bin/sh.

 My code:
 executeShell("diff -u <(echo "~data1~") <(echo "~data2~")");

 Output:
 /bin/sh: 1: Syntax error: "(" unexpected

 This is caused by a limitation from /bin/sh that cannot perform
 process substitution.

 Can this commit be the reason?
 https://github.com/D-Programming-Language/phobos/commit/a524a3571b18e440c4dd751fcf4e2d00b834fb22


Well, based on the information in the corresponding bug report and comments
in the PR, it sounds like it's generally considered best practice to always
use /bin/sh, because it's consistent, whereas who knows what SHELL is set
to. Sure, it's common on Linux systems for it to be bash, but there are
plenty of Linux systems where it isn't, and other POSIX systems like FreeBSD
typically have sh as the default, and many users commonly use shells like
csh or tcsh rather than bash. And of course, the folks who want a
particularly fancy shell use zsh. So, while bash is probably the most
commonly used shell, it's still fairly common for folks to use other shells,
and if you want consistent behavior, you need sh.

That being said, userShell clearly now is inconsistent with its
documentation, and it probably would have been better to just make the other
std.process functions use /bin/sh than to change userShell, since SHELL
really is the user's shell.

Now, if you want to specifically force the use of bash, I think that you're
going to have to use execute or spawnProcess and use /bin/bash as the
command. That's definitely more annoying, but if you look at the
implementation for spawnShell, it sets arguments to pass to spawnProcess to
spawn the shell. executeShell and execute seem more complicated to figure
out how they work, but presumably it's possible to pass a similar command to
execute in order to simulate executeShell with /bin/bash.

- Jonathan M Davis
Sep 01 2015
parent reply "Jonathan M Davis" <jmdavisProg gmx.com> writes:
On Wednesday, 2 September 2015 at 01:26:23 UTC, Jonathan M Davis 
wrote:
[snip]

https://issues.dlang.org/show_bug.cgi?id=15000

- Jonathan M Davis
Sep 01 2015
parent reply "albatroz" <rmcjustino gmail.com> writes:
On Wednesday, 2 September 2015 at 01:46:18 UTC, Jonathan M Davis 
wrote:

 On Wednesday, 2 September 2015 at 01:26:23 UTC, Jonathan M 
 Davis wrote:
 [snip]

 https://issues.dlang.org/show_bug.cgi?id=15000

 - Jonathan M Davis


Thank you for your reply and for the bug report.

Looking at your suggestions I do not fully understand/agree.

executeShell has been one of the easiest ways for us to interact 
with the shell, all other functions require more work to 
implement. Being able to define the shell to be used is something 
that makes sense across all functions in std.process.

Honestly being able to set a different variable name instead of 
SHELL would make more sense. It would not take the default shell 
from the user thus using /bin/sh and would allow us to change it 
if desired with a different value. The change would be minimal 
across code and documentation.

But that's just my suggestion, I'm not a library developer. I 
understand that all variants may have their own issues, but 
taking away from the developer the power to make decisions also 
doesn't seem a good option.

Anyway I would like to ask if you can help to understand why this 
simple example using execute fails?

   auto outputDiff = execute ( ["bash","echo"] );
   writeln (outputDiff.output);

Output:
/bin/echo: /bin/echo: cannot execute binary file

At the moment some of the uses I had are not working and I'm not 
able to implement any workaround.

Obrigado
Sep 02 2015
parent reply Jonathan M Davis via Digitalmars-d-learn writes:
On Wednesday, September 02, 2015 15:28:35 albatroz via Digitalmars-d-learn
wrote:

 On Wednesday, 2 September 2015 at 01:46:18 UTC, Jonathan M Davis
 wrote:

 On Wednesday, 2 September 2015 at 01:26:23 UTC, Jonathan M
 Davis wrote:
 [snip]

 https://issues.dlang.org/show_bug.cgi?id=15000

 - Jonathan M Davis


 Thank you for your reply and for the bug report.

 Looking at your suggestions I do not fully understand/agree.

 executeShell has been one of the easiest ways for us to interact
 with the shell, all other functions require more work to
 implement. Being able to define the shell to be used is something
 that makes sense across all functions in std.process.

 Honestly being able to set a different variable name instead of
 SHELL would make more sense. It would not take the default shell
 from the user thus using /bin/sh and would allow us to change it
 if desired with a different value. The change would be minimal
 across code and documentation.

 But that's just my suggestion, I'm not a library developer. I
 understand that all variants may have their own issues, but
 taking away from the developer the power to make decisions also
 doesn't seem a good option.


Oh, it would be nice to be able to specify the shell (and feel free to add a
comment on that to the bug report). It's just that spawnShell and
executeShell already have a lot of parameters, and it would kind of ugly to
add another. Not to mention, it would probably have to go on the end after
several parameters with default arguments, forcing you to list all of the
default arguments explicitly just so that you can list the shell. So, while
in principle, listing the shell, would be nice. In practice, I'm not sure
how to add it cleanly to the current API, and it _is_ possible to use
execute or spawnProcess to run a specific shell.


 Anyway I would like to ask if you can help to understand why this
 simple example using execute fails?

    auto outputDiff = execute ( ["bash","echo"] );
    writeln (outputDiff.output);

 Output:
 /bin/echo: /bin/echo: cannot execute binary file

 At the moment some of the uses I had are not working and I'm not
 able to implement any workaround.


That's because you're doing the equivalent of

bash echo

on the command line, and if you try that, you'll notice that you get the
same error there. What you need to do instead, per the bash man page, is to
run bash with the -c flag, where -c takes the command you want to run. So,
you can do something like

auto result = execute(["bash", "-c", "echo world"]);

though what gets printed doesn't seem to appear on the command line any more
than if you echoed with executeShell. If you want that, you'd have to use
spawnShell or spawnProcess, e.g.

auto result = wait(spawnProcess(["bash", "-c", "echo world"]));

But if you don't care about the commands appearing on the command line, then
execute works just fine. In either case, the key thing that you're missing
is -c.

- Jonathan M Davis
Sep 02 2015
parent "albatroz" <rmcjustino gmail.com> writes:
On Thursday, 3 September 2015 at 05:07:10 UTC, Jonathan M Davis 
wrote:

 key thing that you're missing is -c.

 - Jonathan M Davis


Hi Jonathan, I would just like to say thank you for the time you 
took to help and clarify.

Obrigado
Sep 03 2015