[gentoo-user] "/usr/bin/[" and coreutils

[gentoo-user] "/usr/bin/[" and coreutils

[William Kenworthy]

I have been checking my system for some deep seated problems and in the
process, ran across the fact that "equery files sys-apps/coreutils-8.7"
shows a file included called "/usr/bin/[" - thats right, left square
bracket!

Is that a bug or if real, what would you use it for?  It doesnt seem to
be on the file system ...

moriah ~ # /usr/bin/[
/usr/bin/[: missing `]'
moriah ~ #

doesnt show much!

BillK

Re: [gentoo-user] "/usr/bin/[" and coreutils

[Canek Peláez Valdés]

On Tue, Oct 11, 2011 at 10:35 PM, William Kenworthy <billk@iinet.net.au> wrote:
> I have been checking my system for some deep seated problems and in the
> process, ran across the fact that "equery files sys-apps/coreutils-8.7"
> shows a file included called "/usr/bin/[" - thats right, left square
> bracket!
>
> Is that a bug or if real, what would you use it for?  It doesnt seem to
> be on the file system ...
>
> moriah ~ # /usr/bin/[
> /usr/bin/[: missing `]'
> moriah ~ #
>
> doesnt show much!

Relax. It's an alias for "test", so instead of using

if test blah; then
...
fi

in bash, you can use

if [ blah ]; then
...
fi

Just do /usr/bin/[ --help to get an idea. It has been there since I
started using Linux, if I remember correctly, many years ago.

Regards.
-- 
Canek Peláez Valdés
Posgrado en Ciencia e Ingeniería de la Computación
Universidad Nacional Autónoma de México

Re: [gentoo-user] "/usr/bin/[" and coreutils

[Manuel McLure]

On Tue, Oct 11, 2011 at 10:35 PM, William Kenworthy <billk@iinet.net.au> wrote:
> I have been checking my system for some deep seated problems and in the
> process, ran across the fact that "equery files sys-apps/coreutils-8.7"
> shows a file included called "/usr/bin/[" - thats right, left square
> bracket!
>
> Is that a bug or if real, what would you use it for?  It doesnt seem to
> be on the file system ...
>
> moriah ~ # /usr/bin/[
> /usr/bin/[: missing `]'
> moriah ~ #
>
> doesnt show much!

'/usr/bin/[' is a synonym for the '/usr/bin/test' utility. It's used
in shell scripts like

if [ -f /etc/passwd ] ; then
  ...

So don't worry. It's supposed to be there.
-- 
Manuel A. McLure WW1FA <manuel@mclure.org> <http://www.mclure.org>
...for in Ulthar, according to an ancient and significant law,
no man may kill a cat.                       -- H.P. Lovecraft

Re: [gentoo-user] "/usr/bin/[" and coreutils

[meino.cramer]

William Kenworthy <billk@iinet.net.au> [11-10-12 07:40]:
> I have been checking my system for some deep seated problems and in the
> process, ran across the fact that "equery files sys-apps/coreutils-8.7"
> shows a file included called "/usr/bin/[" - thats right, left square
> bracket!
> 
> Is that a bug or if real, what would you use it for?  It doesnt seem to
> be on the file system ...
> 
> moriah ~ # /usr/bin/[
> /usr/bin/[: missing `]'
> moriah ~ #
> 
> doesnt show much!
> 
> BillK
> 
> 

Hi Wiiliam,

this is a convenient 'abbreviation' or 'alias' for cobnstructs such this one

if [ foo ] 
then
    bar
fi

in shell scripting.

Most shells have implemented this as a builtin (and 'test' also)
though.

HTH!

Best regards,
mcc

Re: [gentoo-user] "/usr/bin/[" and coreutils

[William Kenworthy]

On Wed, 2011-10-12 at 07:45 +0200, meino.cramer@gmx.de wrote:
> William Kenworthy <billk@iinet.net.au> [11-10-12 07:40]:
> > I have been checking my system for some deep seated problems and in the
> > process, ran across the fact that "equery files sys-apps/coreutils-8.7"
> > shows a file included called "/usr/bin/[" - thats right, left square
> > bracket!
> > 
> > Is that a bug or if real, what would you use it for?  It doesnt seem to
> > be on the file system ...
> > 
> > moriah ~ # /usr/bin/[
> > /usr/bin/[: missing `]'
> > moriah ~ #
> > 
> > doesnt show much!
> > 
> > BillK
> > 
> > 
> 
> Hi Wiiliam,
> 
> this is a convenient 'abbreviation' or 'alias' for cobnstructs such this one
> 
> if [ foo ] 
> then
>     bar
> fi
> 
> in shell scripting.
> 
> Most shells have implemented this as a builtin (and 'test' also)
> though.
> 
> HTH!
> 
> Best regards,
> mcc
> 
> 

GAH! - now I remember ... goes back to my basic unix skills (or lack
of :) - must be getting old ...

Thanks all.

BillK

Re: [gentoo-user] "/usr/bin/[" and coreutils

[Jonas de Buhr]

Am Tue, 11 Oct 2011 22:42:00 -0700
schrieb Canek Peláez Valdés <caneko@gmail.com>:

> On Tue, Oct 11, 2011 at 10:35 PM, William Kenworthy
> <billk@iinet.net.au> wrote:
> > I have been checking my system for some deep seated problems and in
> > the process, ran across the fact that "equery files
> > sys-apps/coreutils-8.7" shows a file included called "/usr/bin/[" -
> > thats right, left square bracket!
> >
> > Is that a bug or if real, what would you use it for?  It doesnt
> > seem to be on the file system ...
> >
> > moriah ~ # /usr/bin/[
> > /usr/bin/[: missing `]'
> > moriah ~ #
> >
> > doesnt show much!
> 
> Relax. It's an alias for "test"

technically it's not an alias, but different binaries

% ls -l /usr/bin/\[
-rwxr-xr-x 1 root root 35096 Jan 20  2011 /usr/bin/[
% ls -l /usr/bin/test
-rwxr-xr-x 1 root root 31000 Jan 20  2011 /usr/bin/test

built from the same source file coreutils/src/test.c with a 
#define LBRACKET
that mainly changes the behavior of the argument parser in case it is
built as [.


>, so instead of using
> 
> if test blah; then
> ...
> fi
> 
> in bash, you can use
> 
> if [ blah ]; then
> ...
> fi
> 
> Just do /usr/bin/[ --help to get an idea. It has been there since I
> started using Linux, if I remember correctly, many years ago.
> 
> Regards.

Re: [gentoo-user] "/usr/bin/[" and coreutils

[Jesús J. Guerrero Botella]

Yes, it's a different binary, and it's perfectly usual to find it in a
Linux system.

But note that, at least in bash, you rarely will be using /usr/bin/[
unless you reference it using the full path (either in a relative or
absolute way). This is because bash has a builtin that takes over that
binary file. You can check that (or any other command) by using the
"type" instruction (again, this is for bash).

# LC_ALL=C type [
[ is a shell builtin

The same goes for 'test'.

Those binaries are probably there just in case that some init or
system script written for a standard bourne shell (like the busybox
one) needs it. But don't take my word for it. I am not sure right now.

-- 
Jesús Guerrero Botella

Re: [gentoo-user] "/usr/bin/[" and coreutils

[Alan McKinnon]

On Thu, 13 Oct 2011 15:38:08 +0200
Jesús J. Guerrero Botella <jesus.guerrero.botella@gmail.com> wrote:

> Yes, it's a different binary, and it's perfectly usual to find it in a
> Linux system.
> 
> But note that, at least in bash, you rarely will be using /usr/bin/[
> unless you reference it using the full path (either in a relative or
> absolute way). This is because bash has a builtin that takes over that
> binary file. You can check that (or any other command) by using the
> "type" instruction (again, this is for bash).
> 
> # LC_ALL=C type [
> [ is a shell builtin
> 
> The same goes for 'test'.
> 
> Those binaries are probably there just in case that some init or
> system script written for a standard bourne shell (like the busybox
> one) needs it. But don't take my word for it. I am not sure right now. 

You might not be sure, but that doesn't stop you still being correct :-)

The binaries are usually POSIX-compliant, whereas the builtins may
include extra bashisms (which tend to break apps expecting just
the basic POSIX behaviour)

-- 
Alan McKinnnon
alan.mckinnon@gmail.com

Re: [gentoo-user] "/usr/bin/[" and coreutils

[Michael Mol]

On Thu, Oct 13, 2011 at 9:50 AM, Alan McKinnon <alan.mckinnon@gmail.com> wrote:
> On Thu, 13 Oct 2011 15:38:08 +0200
> Jesús J. Guerrero Botella <jesus.guerrero.botella@gmail.com> wrote:
>
>> Yes, it's a different binary, and it's perfectly usual to find it in a
>> Linux system.
>>
>> But note that, at least in bash, you rarely will be using /usr/bin/[
>> unless you reference it using the full path (either in a relative or
>> absolute way). This is because bash has a builtin that takes over that
>> binary file. You can check that (or any other command) by using the
>> "type" instruction (again, this is for bash).
>>
>> # LC_ALL=C type [
>> [ is a shell builtin
>>
>> The same goes for 'test'.
>>
>> Those binaries are probably there just in case that some init or
>> system script written for a standard bourne shell (like the busybox
>> one) needs it. But don't take my word for it. I am not sure right now.
>
> You might not be sure, but that doesn't stop you still being correct :-)
>
> The binaries are usually POSIX-compliant, whereas the builtins may
> include extra bashisms (which tend to break apps expecting just
> the basic POSIX behaviour)

I haven't encountered POSIX-dependent apps breaking on bash, but I
have encountered the reverse. My most annoying experience was when I
tried building cinelerra on Debian a few years back. Cinelerra's
script started with #!/bin/sh, but depended on bashisms--and I was
running dash.

-- 
:wq

Re: [gentoo-user] "/usr/bin/[" and coreutils

[Alan McKinnon]

On Thu, 13 Oct 2011 09:59:21 -0400
Michael Mol <mikemol@gmail.com> wrote:

> > The binaries are usually POSIX-compliant, whereas the builtins may
> > include extra bashisms (which tend to break apps expecting just
> > the basic POSIX behaviour)  
> 
> I haven't encountered POSIX-dependent apps breaking on bash, but I
> have encountered the reverse. My most annoying experience was when I
> tried building cinelerra on Debian a few years back. Cinelerra's
> script started with #!/bin/sh, but depended on bashisms--and I was
> running dash.

So you've also run into clueless devs and maintainers who know
almost nothing about shells?

Your example is an extreme one :-), but it's common enough to find
bashisms in scripts with an sh shebang 

-- 
Alan McKinnnon
alan.mckinnon@gmail.com

Re: [gentoo-user] "/usr/bin/[" and coreutils

[Claudio Roberto França Pereira]

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What about [[? I've seen scripts using [[ instead of only one [. Whats the
point/difference?

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Re: [gentoo-user] "/usr/bin/[" and coreutils

[Pandu Poluan]

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On Nov 8, 2011 9:02 AM, "Claudio Roberto França Pereira" <spideybr@gmail.com>
wrote:
>
> What about [[? I've seen scripts using [[ instead of only one [. Whats
the point/difference?

AFAIK [[ was originally a bash-specific built-in command that provides more
functionality than /bin/[, but can still use /bin/['s convoluted syntax.

The two converged quickly, though. IIRC [ is now also a bash built-in,
which still maintains compatibility with /bin/[

An example:

[ $VAR ] will produce an error if VAR is empty or unset, but [[ $VAR ]]
won't.

(for the former, you have to put double quotes around, e.g., [ "$VAR"] )

Rgds,

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Re: [gentoo-user] "/usr/bin/[" and coreutils

[Pandu Poluan]

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On Nov 8, 2011 1:01 PM, "Pandu Poluan" <pandu@poluan.info> wrote:
>
>
> On Nov 8, 2011 9:02 AM, "Claudio Roberto França Pereira" <
spideybr@gmail.com> wrote:
> >
> > What about [[? I've seen scripts using [[ instead of only one [. Whats
the point/difference?
>
> AFAIK [[ was originally a bash-specific built-in command that provides
more functionality than /bin/[, but can still use /bin/['s convoluted
syntax.
>
> The two converged quickly, though. IIRC [ is now also a bash built-in,
which still maintains compatibility with /bin/[
>
> An example:
>
> [ $VAR ] will produce an error if VAR is empty or unset, but [[ $VAR ]]
won't.
>
> (for the former, you have to put double quotes around, e.g., [ "$VAR"] )
>

Uh... of course there should be a space between the second double-quote and
the closing bracket.

Rgds,

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