Debugging with GDB: system

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#### system

Synopsis:

      int system(const char *command);

Request:

  ‘`Fsystem,commandptr/len`’

Return value:

  If len is zero, the return value indicates whether a shell is available. A zero return value indicates a shell is not available. For non-zero len, the value returned is -1 on error and the return status of the command otherwise. Only the exit status of the command is returned, which is extracted from the host’s `system` return value by calling `WEXITSTATUS(retval)`. In case `/bin/sh` could not be executed, 127 is returned.

Errors:
  `EINTR`

    The call was interrupted by the user.

GDB takes over the full task of calling the necessary host calls to perform the `system` call. The return value of `system` on the host is simplified before it’s returned to the target. Any termination signal information from the child process is discarded, and the return value consists entirely of the exit status of the called command.

Due to security concerns, the `system` call is by default refused by GDB. The user has to allow this call explicitly with the `set remote system-call-allowed 1` command.

`set remote system-call-allowed`

  Control whether to allow the `system` calls in the File I/O protocol for the remote target. The default is zero (disabled).

`show remote system-call-allowed`

  Show whether the `system` calls are allowed in the File I/O protocol.