Re: add a way to declare global variables
Bernd Eggink a écrit : To avoid misunderstandings, let me add that you are right (only) with respect to variables being used _without_ declaration. OK, but not having to explicitly declare variables is a feature that most people expect from dynamic languages, so you can hardly blame them for doing this all the time in shell. IMHO Python gets this global/local (implicit) declaration story right. Of course it is easier when you do not have 30 years of POSIX legacy to support (but just the experience). http://docs.python.org/tutorial/controlflow.html#defining-functions
Re: add a way to declare global variables
Am 12/14/09 13:37, schrieb Marc Herbert: Bernd Eggink a écrit : To avoid misunderstandings, let me add that you are right (only) with respect to variables being used _without_ declaration. OK, but not having to explicitly declare variables is a feature that most people expect from dynamic languages, so you can hardly blame them for doing this all the time in shell. I don't blame anybody. I'm talking about the fact that associative arrays are an exception from what most people expect from dynamic languages, as they _have_ to be explicitly declared. This doesn't bother me, but I would prefer to have a choice between local and global declaration anyway. -- Bernd Eggink http://sudrala.de
Re: add a way to declare global variables
Am 12.12.2009 02:11, schrieb Matthew Woehlke: konsolebox wrote: I hope the development team will also consider adding a way in bash to declare global variables inside a function perhaps either with an option in typeset or declare like -g (same as zsh) and/or a builtin function like global as similar to local. I thought variables in functions were /always/ global unless declared local? It's the other way round. Regarding typeset and declare, the man page says: When used in a function, makes each name local, as with the local command. So within a function, typeset, declare, and local are synonyms. Using 'local' outside a function is an error, so IMHO this command is completely redundant. It _would_ make some sense, however, if its counterpart 'global' existed, as it could help clarify the intended usage of the variable. Bernd -- Bernd Eggink http://sudrala.de
Re: add a way to declare global variables
Am 10.12.2009 10:40, schrieb konsolebox: I hope the development team will also consider adding a way in bash to declare global variables inside a function perhaps either with an option in typeset or declare like -g (same as zsh) and/or a builtin function like global as similar to local. I second that. I'm missing this feature badly. Presently, you can only get around this restriction by using a lot of ugly and dangerous 'eval's. Bernd -- Bernd Eggink http://sudrala.de
Re: add a way to declare global variables
On Sat, 12 Dec 2009, Bernd Eggink wrote: Am 12.12.2009 02:11, schrieb Matthew Woehlke: konsolebox wrote: I hope the development team will also consider adding a way in bash to declare global variables inside a function perhaps either with an option in typeset or declare like -g (same as zsh) and/or a builtin function like global as similar to local. I thought variables in functions were /always/ global unless declared local? It's the other way round. Regarding typeset and declare, the man page says: When used in a function, makes each name local, as with the local command. So within a function, typeset, declare, and local are synonyms. Using 'local' outside a function is an error, so IMHO this command is completely redundant. It _would_ make some sense, however, if its counterpart 'global' existed, as it could help clarify the intended usage of the variable. Of the three, local is the only command I use. It says exactly what it does. -- Chris F.A. Johnson, webmaster http://woodbine-gerrard.com === Author: Shell Scripting Recipes: A Problem-Solution Approach (2005, Apress) Pro Bash Programming: Scripting the GNU/Linux Shell (2009, Apress)
Re: add a way to declare global variables
2009-12-12, 11:28(+01), Bernd Eggink: Am 10.12.2009 10:40, schrieb konsolebox: I hope the development team will also consider adding a way in bash to declare global variables inside a function perhaps either with an option in typeset or declare like -g (same as zsh) and/or a builtin function like global as similar to local. I second that. I'm missing this feature badly. Presently, you can only get around this restriction by using a lot of ugly and dangerous 'eval's. [...] For information, zsh has the -g typeset option for that. -- Stéphane
Re: add a way to declare global variables
Am 12.12.2009 11:24, schrieb Bernd Eggink: Am 12.12.2009 02:11, schrieb Matthew Woehlke: konsolebox wrote: I hope the development team will also consider adding a way in bash to declare global variables inside a function perhaps either with an option in typeset or declare like -g (same as zsh) and/or a builtin function like global as similar to local. I thought variables in functions were /always/ global unless declared local? It's the other way round. Regarding typeset and declare, the man page says: When used in a function, makes each name local, as with the local command. So within a function, typeset, declare, and local are synonyms. To avoid misunderstandings, let me add that you are right (only) with respect to variables being used _without_ declaration. The problem is that associative arrays are the only kind of variables that _must_ be declared, since something like a[foo]=bar without a preceding declaration would create an indexed array (and set a[0] to bar). Bernd -- Bernd Eggink http://sudrala.de
Re: add a way to declare global variables
On Dec 12, 4:24 am, Bernd Eggink mono...@sudrala.de wrote:
Am 12.12.2009 02:11, schrieb Matthew Woehlke:
konsolebox wrote:
I hope the development team will also consider adding a way in bash to
declare global variables inside a function perhaps either with an
option in typeset or declare like -g (same as zsh) and/or a builtin
function like global as similar to local.
I thought variables in functions were /always/ global unless declared
local?
It's the other way round. Regarding typeset and declare, the man page
says: When used in a function, makes each name local, as with the
local command. So within a function, typeset, declare, and local are
synonyms. Using 'local' outside a function is an error, so IMHO this
command is completely redundant. It _would_ make some sense, however, if
its counterpart 'global' existed, as it could help clarify the intended
usage of the variable.
Bernd
--
Bernd Egginkhttp://sudrala.de
$ vars () { var1=123; local var2=456; }
$ vars
$ echo var1=$var1 var2=$var2
var1=123 var2=
How is that the other way around?
Re: add a way to declare global variables
2009-12-12, 12:37(-05), Chet Ramey: On 12/12/09 5:24 AM, Bernd Eggink wrote: It's the other way round. Regarding typeset and declare, the man page says: When used in a function, makes each name local, as with the local command. So within a function, typeset, declare, and local are synonyms. Using 'local' outside a function is an error, so IMHO this command is completely redundant. It _would_ make some sense, however, if its counterpart 'global' existed, as it could help clarify the intended usage of the variable. It might be considered redundant, but just consider it a more mnemonic synonym for declare/typeset. `local' appeared in an earlier version of the Posix standard, though `typeset' never did. [...] local is also mandated by the LSB spec for sh as well (Linux standard base). So you can reasonably expect to be able to use it (though only in local varname) on any script meant for a recent Linux sh. -- Stéphane
Re: add a way to declare global variables
On 12/12/09 5:28 AM, Bernd Eggink wrote: Am 10.12.2009 10:40, schrieb konsolebox: I hope the development team will also consider adding a way in bash to declare global variables inside a function perhaps either with an option in typeset or declare like -g (same as zsh) and/or a builtin function like global as similar to local. I second that. I'm missing this feature badly. Presently, you can only get around this restriction by using a lot of ugly and dangerous 'eval's. OK. I'm interested in use cases for this feature. What are you trying to do that you're missing it badly? Chet -- ``The lyf so short, the craft so long to lerne.'' - Chaucer ``Ars longa, vita brevis'' - Hippocrates Chet Ramey, ITS, CWRUc...@case.eduhttp://cnswww.cns.cwru.edu/~chet/
Re: add a way to declare global variables
Am 12.12.2009 21:41, schrieb Chet Ramey: On 12/12/09 5:28 AM, Bernd Eggink wrote: Am 10.12.2009 10:40, schrieb konsolebox: I hope the development team will also consider adding a way in bash to declare global variables inside a function perhaps either with an option in typeset or declare like -g (same as zsh) and/or a builtin function like global as similar to local. I second that. I'm missing this feature badly. Presently, you can only get around this restriction by using a lot of ugly and dangerous 'eval's. OK. I'm interested in use cases for this feature. What are you trying to do that you're missing it badly? One example is introducing some kind of data encapsulation in bash, or even a modest form of object orientation. You may laugh at it, but I think it might be useful in complex scripts. I experimented a little and came up with 'classes' consisting of a function, and 'objects' consisting of a function (representing the interface) plus an equally named associative array (containing the data). The difficulties arise if you want to create an object 'a' of class X by saying X create a You can declare a function 'a' dynamically within function X (using eval), but you can't declare a (global) associative array 'a' there. So that's where a global declaration would be desirable. The alternative is to print the declarations and eval the whole thing in the current environment, but that is very inconvenient and can cause nasty quoting problems. Regards, Bernd -- Bernd Eggink http://sudrala.de
Re: add a way to declare global variables
konsolebox wrote: I hope the development team will also consider adding a way in bash to declare global variables inside a function perhaps either with an option in typeset or declare like -g (same as zsh) and/or a builtin function like global as similar to local. I thought variables in functions were /always/ global unless declared local? -- Matthew Please do not quote my e-mail address unobfuscated in message bodies. -- [Microsoft's] license tells you what a netbook is. -- Steve Ballmer
add a way to declare global variables
Good day, The new feature, associative arrays in bash 4.0 was very useful but I can't find any way to declare them as global when declaring inside a function. By default all variables are set local when using declare and typeset and there are no other ways to declare an associative array but through the said functions. I hope the development team will also consider adding a way in bash to declare global variables inside a function perhaps either with an option in typeset or declare like -g (same as zsh) and/or a builtin function like global as similar to local. Cheers, konsolebox
