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csh() command - pls help

Peter123

 Hi,

Anyone can explain why the setenv command in csh is not working?

 

i got this in my ciw :

csh("setenv JJ \"harlo\"")

 t

When it returned a "t", meant the csh command is executed sucessfully.

 when i did a echo $JJ in my work dir...

I got this :

JJ: Undefined variable

 

Any one can explain why...

 

Thanks,

-p-

 

Parents
  • Andrew Beckett
    Because that is not how UNIX works.

    When you launch virtuoso/icfb it is a child process of the shell you started it in. It inherits the environment (eg env vars) from the parent shell. Any env var you change in virtuoso (eg using the SKILL function setShellEnvVar()) will not affect the parent process, but will affect any child processes launched by virtuoso.

    When you launch csh("setenv ...") you are in fact starting yet another process (a grandchild of the shell you started) so that's even further way from affecting the parent.

    Even if you were in the terminal window and did "csh -c 'setenv JJ harlo'" it would not affect what you see in the terminal, because that too is a child process. (Note that csh command line I did not test, but I think the -c syntax is correct)

    Fundamentally child processes cannot affect the environment of their parent.

    Regards,

    Andrew
Reply
  • Andrew Beckett
    Because that is not how UNIX works.

    When you launch virtuoso/icfb it is a child process of the shell you started it in. It inherits the environment (eg env vars) from the parent shell. Any env var you change in virtuoso (eg using the SKILL function setShellEnvVar()) will not affect the parent process, but will affect any child processes launched by virtuoso.

    When you launch csh("setenv ...") you are in fact starting yet another process (a grandchild of the shell you started) so that's even further way from affecting the parent.

    Even if you were in the terminal window and did "csh -c 'setenv JJ harlo'" it would not affect what you see in the terminal, because that too is a child process. (Note that csh command line I did not test, but I think the -c syntax is correct)

    Fundamentally child processes cannot affect the environment of their parent.

    Regards,

    Andrew
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