Re: [Tutor] Confirmation if command worked
On 2011/08/25 07:51 AM, Johan Geldenhuys wrote: Hi all, I have the following code that uses pexpect to execute a system command. My problem is, I don't know how to identify if the command was successfully executed. The code works as it is to execute the SCP command, but it executes regardless if the SCP session can actually connect to something. Thanks def doScp(files): logger.log(Files to get: + `files`) fNames = ' '.join(files) cmd = 'scp %s %s@%s:%s%s' % (fNames, SCP_USERNAME, SCP_HOST, SCP_IMG_FILE_DIR, SCP_IMG_FILE_PATH) logger.log(Sending: + cmd) child = pexpect.spawn(cmd) i = child.expect(['assword:', 'yes/no'], timeout=30) if i == 0: child.sendline(SCP_PASSWD) elif i == 1: child.sendline(yes) child.expect(assword:, timeout=30) child.sendline(SCP_PASSWD) data = child.read() if data != None: success = True else: success = False child.close() logger.log(Files sent to SCP host) return success ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor Once you call child.close() the exit and signal status will be stored in .exitstatus and .signalstatus, for a normal exit of the program .exitstatus will store the return code from SCP as per [1] [2] [3] and .signalstatus will be None. If SCP was terminated with a signal then .exitstatus will be None and .signalstatus will contain the signal value. Info found in the docs [4]. So the changes to your code will be: snip data = child.read() child.close() if child.exitstatus and child.exitstatus == 0: success = True else: success = False snip I'll leave putting in handling of failed error codes and abnormal termination to you. [1] http://support.attachmate.com/techdocs/2116.html [2] http://support.attachmate.com/techdocs/2487.html [3] http://support.attachmate.com/techdocs/2285.html [4] http://pexpect.sourceforge.net/pexpect.html -- Christian Witts Python Developer // ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Confirmation if command worked
Hi Christian, Thanks for that. I'll give it a shot and see if I can catch the error. Lekker dag Johan From: Christian Witts [mailto:cwi...@compuscan.co.za] Sent: Thursday, 25 August 2011 4:25 PM To: Johan Geldenhuys Cc: tutor@python.org Subject: Re: [Tutor] Confirmation if command worked On 2011/08/25 07:51 AM, Johan Geldenhuys wrote: Hi all, I have the following code that uses pexpect to execute a system command. My problem is, I don't know how to identify if the command was successfully executed. The code works as it is to execute the SCP command, but it executes regardless if the SCP session can actually connect to something. Thanks def doScp(files): logger.log(Files to get: + `files`) fNames = ' '.join(files) cmd = 'scp %s %s@%s:%s%s' % (fNames, SCP_USERNAME, SCP_HOST, SCP_IMG_FILE_DIR, SCP_IMG_FILE_PATH) logger.log(Sending: + cmd) child = pexpect.spawn(cmd) i = child.expect(['assword:', 'yes/no'], timeout=30) if i == 0: child.sendline(SCP_PASSWD) elif i == 1: child.sendline(yes) child.expect(assword:, timeout=30) child.sendline(SCP_PASSWD) data = child.read() if data != None: success = True else: success = False child.close() logger.log(Files sent to SCP host) return success ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor Once you call child.close() the exit and signal status will be stored in .exitstatus and .signalstatus, for a normal exit of the program .exitstatus will store the return code from SCP as per [1] [2] [3] and .signalstatus will be None. If SCP was terminated with a signal then .exitstatus will be None and .signalstatus will contain the signal value. Info found in the docs [4]. So the changes to your code will be: snip data = child.read() child.close() if child.exitstatus and child.exitstatus == 0: success = True else: success = False snip I'll leave putting in handling of failed error codes and abnormal termination to you. [1] http://support.attachmate.com/techdocs/2116.html [2] http://support.attachmate.com/techdocs/2487.html [3] http://support.attachmate.com/techdocs/2285.html [4] http://pexpect.sourceforge.net/pexpect.html -- Christian Witts Python Developer ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Confirmation if command worked
On 25/08/11 07:25, Christian Witts wrote: Once you call child.close() the exit and signal status will be stored in .exitstatus and .signalstatus, for a normal exit of the program .exitstatus will store the return code from SCP as per [1] [2] [3] and .signalstatus will be None. If SCP was terminated with a signal then .exitstatus will be None and .signalstatus will contain the signal value. Info found in the docs [4]. data = child.read() child.close() if child.exitstatus and child.exitstatus == 0: success = True else: success = False Won't that if statement always evaluate to false? If exitstatus is 0 the first part of the and will be false and so the entire and expression is false. If exitstatus is not 0 then the second part of the and will be false and again the and result will be false. Did you mean to use exitstatus for both tests? Or am I missing something subtle here? -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Confirmation if command worked
On 2011/08/25 10:19 AM, Alan Gauld wrote: On 25/08/11 07:25, Christian Witts wrote: Once you call child.close() the exit and signal status will be stored in .exitstatus and .signalstatus, for a normal exit of the program .exitstatus will store the return code from SCP as per [1] [2] [3] and .signalstatus will be None. If SCP was terminated with a signal then .exitstatus will be None and .signalstatus will contain the signal value. Info found in the docs [4]. data = child.read() child.close() if child.exitstatus and child.exitstatus == 0: success = True else: success = False Won't that if statement always evaluate to false? If exitstatus is 0 the first part of the and will be false and so the entire and expression is false. If exitstatus is not 0 then the second part of the and will be false and again the and result will be false. Did you mean to use exitstatus for both tests? Or am I missing something subtle here? Good catch, it should be `if child.exitstatus != None and child.exitstatus == 0:` or removing the first part entirely. The zero-evaluating-as-False has bitten me before and for some reason I still on occasion forget it even though I use it often for data extracts. -- Christian Witts Python Developer // ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Confirmation if command worked
On 25-Aug-11 01:37, Christian Witts wrote: Good catch, it should be `if child.exitstatus != None and child.exitstatus == 0:` It's better form to say if child.exitstatus is not None instead of comparing for equality to None with the != operator. -- Steve Willoughby / st...@alchemy.com A ship in harbor is safe, but that is not what ships are built for. PGP Fingerprint 4615 3CCE 0F29 AE6C 8FF4 CA01 73FE 997A 765D 696C ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Confirmation if command worked
Christian Witts wrote: if child.exitstatus and child.exitstatus == 0: success = True else: success = False There is never any need to write Python code that looks like that. (Or in any other language I'm familiar with either.) Anything of the form: if some_condition: flag = True else: flag = False is better written as: flag = some_condition In the above example, you should write: success = child.exitstatus and child.exitstatus == 0 except that I think you have the condition wrong... if exitstatus is zero, you get False and True = False, but if exitstatus is non-zero, you get True and False = False. So you will always get success = False. -- Steven ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Confirmation if command worked
Steven D'Aprano wrote: if some_condition: flag = True else: flag = False is better written as: flag = some_condition Actually, that's a slight over-simplification. some_condition may not actually be a bool. If you don't mind flag also being a non-bool, that's fine, but if you want to ensure that it is one of True/False, then you can call: flag = bool(some_condition) to force flag to be one of True or False. But that's generally not necessary unless you care about what flag looks like when printed. -- Steven ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
[Tutor] Confirmation if command worked
Hi all, I have the following code that uses pexpect to execute a system command. My problem is, I don't know how to identify if the command was successfully executed. The code works as it is to execute the SCP command, but it executes regardless if the SCP session can actually connect to something. Thanks def doScp(files): logger.log(Files to get: + `files`) fNames = ' '.join(files) cmd = 'scp %s %s@%s:%s%s' % (fNames, SCP_USERNAME, SCP_HOST, SCP_IMG_FILE_DIR, SCP_IMG_FILE_PATH) logger.log(Sending: + cmd) child = pexpect.spawn(cmd) i = child.expect(['assword:', 'yes/no'], timeout=30) if i == 0: child.sendline(SCP_PASSWD) elif i == 1: child.sendline(yes) child.expect(assword:, timeout=30) child.sendline(SCP_PASSWD) data = child.read() if data != None: success = True else: success = False child.close() logger.log(Files sent to SCP host) return success ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
