[GitHub] [incubator-nuttx-apps] xiaoxiang781216 edited a comment on issue #185: nsh improvement

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xiaoxiang781216 edited a comment on issue #185: nsh improvement
URL: https://github.com/apache/incubator-nuttx-apps/pull/185#issuecomment-615844029
 
 
   > There is a logic flaw in hsow system() is called. The system() call will block until the cmd is executed. Any & or redirection on the command will not be handled. Too much breakage! That is not acceptable and must be fixed.
   > 
   
   But the old implementation call nsh_script directly, which also block until the script finish execution. If the old behaviour support &, then the new should support too, because the only difference is that the new one has a longer call chain:
   new: cmd_sh->system->posix_task->nsh_system->nsh_parse->nsh_source->nsh_script
   old: cmd_sh->nsh_script
   The real action happen inside nsh_script, so the key is that nsh_script need to enhance to support &.
   
   > Hmmm... Or does the system command run on a pthread via cmd_sh(). In that case, then the & background option would work (although it ties up both a pthread and a task).
   > 
   
   Should we put the logic into nsh_script? since we have support:
   sh /path/to/script &
   source /path/to/script &
   Both will call nsh_script finally.
   
   > But the redirection as it is implemented for cmd_sh() will not work for system(cmd). Within NSH, redirection is handled via nsh_output(), stdin/stdout/stderr are not changed.
   > 
   
   Yes, if the redirection just change the internal parser state not stdin/stdtout/stderr, the new nsh task can't inherit the redirection setting.
   
   > So even though you redirect the output at cmd_sh, will not be redirected by system(). This is not good. This is a good idea but not ready to come into the master.
   
   How about we modify stdin/stdout/stderr directly?

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