Comprehensive comparison between zsh and bash

Comprehensive comparison between zsh and bash

[Peng Yu]

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I’d like to migrate some of my bash scripts to zsh. (Therefore, I don’t
care the difference in the interactive mode.) But there are still many
subtle differences between bash and zsh in the non-interactive part.

Because I’d like to make the migration as painless as possible, it is
better to have a comprehensive list of difference between bash and zsh
along with the functional equivalent code upfront. I don’t find such a
comprehensive list yet. But is there a list that is at least close to
comprehensive to ease the migration?

Thanks.
-- 
Regards,
Peng

Re: Comprehensive comparison between zsh and bash

[Eric Cook]

On 7/5/19 4:01 PM, Peng Yu wrote:
> But is there a list that is at least close to
> comprehensive to ease the migration?
>
> Thanks.
>

Nope.

Re: Comprehensive comparison between zsh and bash

[Ray Andrews]

On 2019-07-05 1:01 p.m., Peng Yu wrote:
> I’d like to migrate some of my bash scripts to zsh. (Therefore, I don’t
> care the difference in the interactive mode.) But there are still many
> subtle differences between bash and zsh in the non-interactive part.

Just curious:  Is there some way of dumping the state of all variables 
at all lines with both bash and zsh to some file or other such that one 
could quickly spot exactly when and where something might change between 
them?  Not a proactive, analytic study of the code, but just a pragmatic 
finding of differences after the fact.

Re: Comprehensive comparison between zsh and bash

[Phil Pennock]

On 2019-07-05 at 13:29 -0700, Ray Andrews wrote:
> Just curious:  Is there some way of dumping the state of all variables at
> all lines with both bash and zsh to some file or other such that one could
> quickly spot exactly when and where something might change between them? 
> Not a proactive, analytic study of the code, but just a pragmatic finding of
> differences after the fact.

`typeset -p` dumps all variables; the format differs slightly between
shells but that's light text-munging to normalize.

This is probably a good start:

    trap 'typeset -p' DEBUG

although I'm not going to promise that the DEBUG hook is invoked in
exactly the same circumstances in each shell.  But that should get you
going.  It will be voluminous.

You might consider:

    mkdir -m 0700 -p "$HOME/traces"
    exec 4>"$HOME/traces/$$.log"
    trap 'typeset -p >&4' DEBUG

You could use `set -x` too, to see the commands being run, but while
bash has `BASH_XTRACEFD`, I don't think zsh has anything quite like
that.  So you're going to lose stderr, or accept differences.

-Phil

Re: Comprehensive comparison between zsh and bash

[Ray Andrews]

On 2019-07-05 7:31 p.m., Phil Pennock wrote:
> On 2019-07-05 at 13:29 -0700, Ray Andrews wrote:
>> Just curious:  Is there some way of dumping the state of all variables at
>> all lines with both bash and zsh to some file or other such that one could
>> quickly spot exactly when and where something might change between them?
>> Not a proactive, analytic study of the code, but just a pragmatic finding of
>> differences after the fact.
> `typeset -p` dumps all variables; the format differs slightly between
> shells but that's light text-munging to normalize.
>
> This is probably a good start:
>
>      trap 'typeset -p' DEBUG

Thanks Phil and Sebastian.  I have no need for it myself since I've 
never done a thing in bash, but I was wondering what might be available 
to converts.  I'll play with your suggestions anyway tho just for fun.  
But since all the other shells are moribund it seems to me that zsh 
should make an effort to draw all shellers to itself and to make room 
around the fire for them.  It would add to critical mass and maybe spark 
some innovation.  Maybe there could be some purpose build conversion 
utilities.

Re: Comprehensive comparison between zsh and bash

[Sebastian Gniazdowski]

On Fri, 5 Jul 2019 at 22:31, Ray Andrews <rayandrews@eastlink.ca> wrote:
> Just curious:  Is there some way of dumping the state of all variables
> at all lines with both bash and zsh to some file or other such that one
> could quickly spot exactly when and where something might change between
> them?  Not a proactive, analytic study of the code, but just a pragmatic
> finding of differences after the fact.

Maybe this plugin could help? https://github.com/psprint/zsnapshot

-- 
Sebastian Gniazdowski
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