Re: Bash does not read up the whole script which it is currently executing
On Aug 5, 2:05 pm, Marc Herbert marc.herbert+n...@gmail.com wrote: I am not sure I get this... first of all, the script itself is usually not read from stdin (but from fd 255 in bash). Now considering the seldom cases where the script is actually read from stdin, are you saying that: it is a wanted feature that subprocesses can concurrently slurp and steal the code executed by their parent? Wow, that sounds really weird and not something I would wish, but rather a design limitation that I should constantly worry about. Regards, Marc Same here, as Marc said. I think that usually we are reading the script from a file and this is the use-case we must focus on. Currently, we have the problem I described when executing a script from a file and I think this must be fixed/changed. --Ivan John Reiser wrote: On 08/04/2009 12:48 AM, fam...@icdsoft.com wrote: It is an intended design feature that the shell reads only as much as necessary to proceed at the moment. This is required so that subprocesses can share the same stdin as the shell. Bytes for input to the shell alternate with bytes for input to each subprocess that does not have redirection (or closure) specified for its stdin. To avoid this feature, then use the -c parameter to specify the entire shell input as a string on the command line: bash -c $( filename) Or, make a temporary unique copy of the file, then invoke the shell on the copy.
Re: Bash does not read up the whole script which it is currently executing
Ivan Zahariev a écrit : Same here, as Marc said. I think that usually we are reading the script from a file and this is the use-case we must focus on. Currently, we have the problem I described when executing a script from a file and I think this must be fixed/changed. Hey, wait. I am not saying that this must be changed. I can imagine there are good reasons for the current behaviour (like for instance performance or conformance). Just not the reason put by John.
Re: Bash does not read up the whole script which it is currently executing
John Reiser a écrit : On 08/04/2009 12:48 AM, fam...@icdsoft.com wrote: First I would like to say that I'm not sure if this is a bug or a feature of Bash. If it is a feature, please let me know how to turn it off; or better make it disabled by default... The problem is that Bash does not read up the whole script which it is currently executing. As a result of this, if we update the script file with a newer version while it is running, this may lead to unpredicted results. It is an intended design feature that the shell reads only as much as necessary to proceed at the moment. This is required so that subprocesses can share the same stdin as the shell. Bytes for input to the shell alternate with bytes for input to each subprocess that does not have redirection (or closure) specified for its stdin. I am not sure I get this... first of all, the script itself is usually not read from stdin (but from fd 255 in bash). Now considering the seldom cases where the script is actually read from stdin, are you saying that: it is a wanted feature that subprocesses can concurrently slurp and steal the code executed by their parent? Wow, that sounds really weird and not something I would wish, but rather a design limitation that I should constantly worry about. Regards, Marc
Re: Bash does not read up the whole script which it is currently executing
On 08/04/2009 12:48 AM, fam...@icdsoft.com wrote: First I would like to say that I'm not sure if this is a bug or a feature of Bash. If it is a feature, please let me know how to turn it off; or better make it disabled by default... The problem is that Bash does not read up the whole script which it is currently executing. As a result of this, if we update the script file with a newer version while it is running, this may lead to unpredicted results. It is an intended design feature that the shell reads only as much as necessary to proceed at the moment. This is required so that subprocesses can share the same stdin as the shell. Bytes for input to the shell alternate with bytes for input to each subprocess that does not have redirection (or closure) specified for its stdin. To avoid this feature, then use the -c parameter to specify the entire shell input as a string on the command line: bash -c $( filename) Or, make a temporary unique copy of the file, then invoke the shell on the copy. --
Re: Bash does not read up the whole script which it is currently executing
On Tue, Aug 04, 2009 at 08:23:16AM -0700, John Reiser wrote: On 08/04/2009 12:48 AM, fam...@icdsoft.com wrote: The problem is that Bash does not read up the whole script which it is currently executing. As a result of this, if we update the script file with a newer version while it is running, this may lead to unpredicted results. To avoid this feature, then use the -c parameter to specify the entire shell input as a string on the command line: bash -c $( filename) Or, make a temporary unique copy of the file, then invoke the shell on the copy. Or upgrade your scripts like this: mv -f /path/to/script /path/to/script.old cp newscript /path/to/script (Or remove-then-copy, or make /path/to/script a symlink to a version-stamped copy, or any number of other ways that are not vi /path/to/script.)
