Experimental Physics and
Industrial Control System

"Johnson, Andrew N. via Core-talk" <core-talk at aps.anl.gov> · Wed, 14 Apr 2021 16:56:26 +0000

Hi Ralph,

On Apr 14, 2021, at 11:13 AM, Ralph Lange via Core-talk <core-talk at aps.anl.gov> wrote:
> 
> AppData is one of quite a few standard Windows variables. Obviously, introducing my own variables would work and make the whole thing non-portable.
> 
> The getenv() call works just fine, mixed paths work fine, I can read directly from the environment and have utilities that convert forward to backslashes etc etc.
> The one and only real show stopper is that the iocShell's macro expansion changes the value of those standard environment variables when you use them.

Even epicsEnvSet preserves back-slashes in the values it sets. The macLib routines are supposed to preserve strings inside single quotes, but then they don’t expand the macros inside. I just experimented with various ways of quoting stuff, but that doesn’t seem to help at all:

> epics> epicsEnvShow APPDATA
> APPDATA=C:\Users\jenkins\AppData\Roaming

> epics> echo $(APPDATA)
> C:UsersjenkinsAppDataRoaming
> epics> echo "$(APPDATA)”
> C:UsersjenkinsAppDataRoaming
> epics> echo '$(APPDATA)' 
> $(APPDATA)
> epics> epicsEnvSet q "'"
> epics> epicsEnvShow q
> q='
> epics> echo $(q)$(APPDATA)$(q)
> C:UsersjenkinsAppDataRoaming
> epics> echo "$(q)$(APPDATA)$(q)" 
> C:UsersjenkinsAppDataRoaming
> epics> epicsEnvSet eq "\'"       
> epics> epicsEnvShow eq           
> eq=\'
> epics> echo "$(eq)$(APPDATA)$(eq)" 
> 'C:UsersjenkinsAppDataRoaming'
> epics> epicsEnvSet d '"'           
> epics> epicsEnvShow d              
> d="
> epics> echo "$(d)$(APPDATA)$(d)"   
> C:UsersjenkinsAppDataRoaming
> epics> epicsEnvSet b "\"
> epics> epicsEnvShow b
> b=\
> epics> echo "$(b)$(APPDATA)$(b)"       
> C:UsersjenkinsAppDataRoaming
> epics> epicsEnvSet bb "\\"       
> epics> epicsEnvShow bb           
> bb=\\
> epics> echo "$(bb)$(APPDATA)$(bb)" 
> C:UsersjenkinsAppDataRoaming
> epics> epicsEnvSet bbb "\\\"       
> epics> epicsEnvShow bbb            
> bbb=\\\
> epics> echo "$(bbb)$(APPDATA)$(bbb)" 
> \C:UsersjenkinsAppDataRoaming\
> epics> epicsEnvSet ed '\"'         
> epics> epicsEnvShow ed           
> ed=\"
> epics> echo "$(ed)$(APPDATA)$(ed)" 
> C:UsersjenkinsAppDataRoaming
> epics> epicsEnvSet eeq "\\'"           
> epics> epicsEnvShow eeq                
> eeq=\\'
> epics> echo "$(eeq)$(APPDATA)$(eeq)"   
> C:UsersjenkinsAppDataRoaming
> epics> epicsEnvSet eeeq "\\\'"       
> epics> epicsEnvShow eeeq             
> eeeq=\\\'
> epics> echo "$(eeeq)$(APPDATA)$(eeeq)" 
> 'C:UsersjenkinsAppDataRoaming’
> epics> epicsEnvSet eed '\\"'        
> epics> epicsEnvShow eed            
> eed=\\"
> epics> echo "$(eed)$(APPDATA)$(eed)" 
> C:UsersjenkinsAppDataRoaming
> epics> epicsEnvSet eeed '\\\"'       
> epics> epicsEnvShow eeed             
> eeed=\\\"
> epics> echo "$(eeed)$(APPDATA)$(eeed)" 
> Unbalanced quote.

That last error (from iocsh, not macLib) is interesting, but probably not useful.

Do we need some syntax in macros to prevent them from escaping back-slashes when expanding values?  I’m not sure how easy it would be to implement that, but it might be possible. Any other suggestions on what might be changed?

- Andrew

-- 
Complexity comes for free, simplicity you have to work for.

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System