Is it possible to make system use bash instead of sh?

Ruby
#1

Hi,

Does anyone know if it is possible to use bash instead of sh as the
default shell when “system” is executed?

For example, system(“java --version”) is executing java --version in sh,
instead of bash, which can be a problem when I tried to do error
redirection.

#2

On 4/25/07, Wai T. [email protected] wrote:

Posted via http://www.ruby-forum.com/.

If bash is in your path you can do
system(“bash -c “java -version””)
else you just have to put the full path, this works even on Windows :slight_smile:

Of course that is not exactly what you want, you would like to tell
Kernel or whatever other object that wants to hear that kind of
message: “You are going to use /bin/bash for system from now on”.
So I went digging the code, no such luck, I just could not find the
definition of Kernel#system :frowning:
neither with rb_define_method.system
nor with def\ssystem
and even less with
alias\s*system
or
rb_alias.*system
Hope that somebody more learned will help us out here.

Cheers
Robert

#3

On Thu, Apr 26, 2007 at 12:18:04AM +0900, Wai T. wrote:

Does anyone know if it is possible to use bash instead of sh as the
default shell when “system” is executed?

system() with multiple arguments bypasses the shell. So try:

system("/bin/bash", “-c”, “java --version”)

#4

-----BEGIN PGP SIGNED MESSAGE-----

In article
[email protected],
Robert D. [email protected] wrote:

alias\s*system
or
rb_alias.*system
Hope that somebody more learned will help us out here.

_ Ruby uses the underlying C exec call and any system that does
not use /bin/sh is severely broken. It’s part of the POSIX
standard. If you want bash, then use the multi-arg form of the
command which bypasses shell interpretation entirely.

If you want the gory details look in process.c

rb_f_system

_ Booker C. Bense

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#5

On 4/25/07, Booker C. Bense

If you want the gory details look in process.c

rb_f_system

Thx a lot, that’s what I was looking for…

#6

On Apr 25, 2007, at 11:18 AM, Wai T. wrote:

Hi,

Does anyone know if it is possible to use bash instead of sh as the
default shell when “system” is executed?
Whenever ‘system’ is executed? Not sure about that. But what you
might be able to do is have a new file that stores code which defines
‘system2’, and you could include that. It might be something like:

def system2(command)
system ‘bash’
system '#{command}
end

Of course, i have no clue (yet) how to use #{stuff} in my code, so
any help would automatically be worthy of worship.

Oh, and same with having two parameters in ‘do’ commands. Help? Please?

HTH
-------------------------------------------------------|
~ Ari
crap my sig won’t fit

#7

Thanks. System(‘bash’,’-c’,cmd) does the task for me.

#8

On Thu, Apr 26, 2007 at 01:46:25AM +0900, Gary W. wrote:

This behavior with respect to the Single Unix
Specification is documented at:

http://www.opengroup.org/onlinepubs/007908799/xsh/system.html

Standards like the Single Unix Specification (and the LSB, and so on)
should be used as reasons for standardized behavior in a distributed
OS, but they aren’t really relevant to customized installs. If an end
user wants to configure a system differently from the standard, that’s
his/her business.

#9

On Apr 25, 2007, at 4:24 PM, Chad P. wrote:

user wants to configure a system differently from the standard, that’s
his/her business.

I didn’t see anyone claiming differently. I certainly wasn’t. I just
perceived the question as a desire for information about the standard.

#10

Wai T. [email protected] writes:

Hi,

Does anyone know if it is possible to use bash instead of sh as the
default shell when “system” is executed?

For example, system(“java --version”) is executing java --version in sh,
instead of bash, which can be a problem when I tried to do error
redirection.

–

Others have indicated how you can execute the command with bash rather
than sh.
However, I’m interested in why you have problems with redirecting
standard
error with sh bat not bash. While I seem to remember bash offers some
additional functionality, I thought redirecting of stdin/stdout/stderr
was
pretty similar, if not in syntax at least in functionality. Also, its
been some
time since I did java, but from memory, it uses quite a few shell
wrapper
scripts and they are all in sh rather than bash.

Just interested.

tim

#11

On 25.04.2007 17:43, Björn Paetzel wrote:

Wai T. schrieb:

Does anyone know if it is possible to use bash instead of sh as the
default shell when “system” is executed?

System() should always call /bin/sh (on a POSIX compliant system),

Where did you get that information from?

but
of course you could still have sh call bash, like this:

system(“bash java --version”)

Yes, of course.

robert

#12

On Apr 25, 2007, at 12:00 PM, Robert K. wrote:

On 25.04.2007 17:43, Björn Paetzel wrote:

Wai T. schrieb:

Does anyone know if it is possible to use bash instead of sh as the
default shell when “system” is executed?
System() should always call /bin/sh (on a POSIX compliant system),

Where did you get that information from?

This behavior with respect to the Single Unix
Specification is documented at:

http://www.opengroup.org/onlinepubs/007908799/xsh/system.html

Gary W.

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