Python Conditional Statements Based on Success of Last Command Post: 302867715

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Top Forums Programming Python Conditional Statements Based on Success of Last Command Post 302867715 by alister on Thursday 24th of October 2013 08:05:00 PM

10-24-2013

Registered User

Hi, wisecracker.

From the python os.system documentation:

Code:

On Unix, the return value is the exit status of the process encoded in the format specified for wait().

You should read the man page for the wait(2) system call. The integer returned, (32512 above) encodes more information than just the value passed to the exit system call. There are macros that are used to extract the actual value passed to exit(). Python's os module provides access to those macros. The two most relevant to your post:

Code:

os.WIFEXITED(status)

    Return True if the process exited using the exit(2) system call, otherwise return False.

    Availability: Unix.

os.WEXITSTATUS(status)

    If WIFEXITED(status) is true, return the integer parameter to the exit(2) system call.
    Otherwise, the return value is meaningless.

    Availability: Unix.

Those excerpts are from Python Standard Library - 16.1 - os.

To summarize, you cannot directly read the integer returned by wait(2) (which is the return value of os.system on UNIX). Also, you should not use bit shifting and/or masking to extract the relevant status bits because the encoding is allowed to differ between system implementations.

Regards,
Alister

Last edited by alister; 10-24-2013 at 09:15 PM..

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execute

EXECUTE(7)							   SQL Commands 							EXECUTE(7)

NAME

       EXECUTE - execute a prepared statement

SYNOPSIS

       EXECUTE name [ ( parameter [, ...] ) ]

DESCRIPTION

       EXECUTE	is  used  to execute a previously prepared statement. Since prepared statements only exist for the duration of a session, the pre-
       pared statement must have been created by a PREPARE statement executed earlier in the current session.

       If the PREPARE statement that created the statement specified some parameters, a compatible set of parameters must be passed to the EXECUTE
       statement,  or  else an error is raised. Note that (unlike functions) prepared statements are not overloaded based on the type or number of
       their parameters; the name of a prepared statement must be unique within a database session.

       For more information on the creation and usage of prepared statements, see PREPARE [prepare(7)].

PARAMETERS

       name   The name of the prepared statement to execute.

       parameter
	      The actual value of a parameter to the prepared statement. This must be an expression yielding a value that is compatible  with  the
	      data type of this parameter, as was determined when the prepared statement was created.

OUTPUTS

       The command tag returned by EXECUTE is that of the prepared statement, and not EXECUTE.

EXAMPLES

       Examples are given in the Examples [prepare(7)] section of the PREPARE [prepare(7)] documentation.

COMPATIBILITY

       The  SQL  standard includes an EXECUTE statement, but it is only for use in embedded SQL. This version of the EXECUTE statement also uses a
       somewhat different syntax.

SEE ALSO

       DEALLOCATE [deallocate(7)], PREPARE [prepare(7)]

SQL - Language Statements					    2010-05-14								EXECUTE(7)

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