21.4.1 Setting of specified command execution

This section explains how to use commandline module to execute the specified command.

Commandline module has a CommandLine class that executes configuration and operation commands from scripts. The following tables list the methods for CommandLine classes.

Table 21-15 List of Methods of the CommandLine Class
Method name	Description
exec	Executes the command specified in the argument.
exit	Terminates command execution by the instance.
set_default_timeout	Sets the default timeout period when the command is executed by the target instance.
set_default_logging	Specifies whether or not the operation command show logging is to be displayed for logging commands executed from the target instance.

<Structure of this section>

(1) Script file and execution results example

(a) Examples of executing various commands

Here is an example of a script file that executes various commands:

Figure 21-15: Example of writing a script file (sample1.py)
# sample1.py # -- coding: utf-8 -- import extlib.commandline ..1 obj = extlib.commandline.CommandLine() ..2 # Specify default timeout obj.set_default_timeout(180) ..3 # Specify default non-display of command log show logging obj.set_default_logging(extlib.commandline.DISABLE) ..4 # User-unresponsive command (ls) print("ls start") dict_ret = obj.exec("ls") ..5 if dict_ret['result'] == extlib.commandline.OK: print(dict_ret['strings']) ..6 else: print("timeout.") # Command with user response (delete file1, file2) print("rm start") dict_ret = obj.exec("rm -i file1 file2", ("?","y"), ("?", "y"), logging=extlib.commandline.ENABLE) ..7 if dict_ret['result'] == extlib.commandline.OK: print(dict_ret['strings']) ..8 else: print("timeout.") # Specify command response timeout period (ping for 3 sec) print("ping start") dict_ret = obj.exec("ping 192.0.2.1", 3) ..9 if dict_ret['result'] == extlib.commandline.TIMEOUT: print(dict_ret['strings']) ..10 obj.exit() ..11

Figure 21-15: Example of writing a script file (sample1.py)

# sample1.py
# -*- coding: utf-8 -*-
import extlib.commandline                                             ..1
obj = extlib.commandline.CommandLine()                                ..2
 
# Specify default timeout
obj.set_default_timeout(180)                                          ..3
 
# Specify default non-display of command log show logging
obj.set_default_logging(extlib.commandline.DISABLE)                   ..4
 
# User-unresponsive command (ls) 
print("ls start")
dict_ret = obj.exec("ls")                                             ..5
if dict_ret['result'] == extlib.commandline.OK:
    print(dict_ret['strings'])                                        ..6
else:
    print("timeout.")
 
# Command with user response (delete file1, file2) 
print("rm start")
dict_ret = obj.exec("rm -i file1 file2", ("?","y"), ("?", "y"),
                     logging=extlib.commandline.ENABLE)               ..7
if dict_ret['result'] == extlib.commandline.OK:
    print(dict_ret['strings'])                                        ..8
else:
    print("timeout.")
 
# Specify command response timeout period (ping for 3 sec) 
print("ping start")
dict_ret = obj.exec("ping 192.0.2.1", 3)                              ..9
if dict_ret['result'] == extlib.commandline.TIMEOUT:
    print(dict_ret['strings'])                                        ..10
obj.exit()                                                            ..11

Import the module.
Creates an instance of CommandLine.
Specifies the default timeout period for command responses.
Hides the default show logging display setting for the command log.
In exec method, specify the command to be executed (no user response).
Outputs the command execution result.
In exec method, specify the command to be executed (with user response) and show logging view setting (display) of the command log.
Outputs the command execution result.
In exec method, specify the timeout period for the command to be executed and the command response.
Outputs the command execution result.
Ends the command execution status.

The script file sample1.py executes as follows: The operation-command ls,rm, and ping specified in exec method are executed correctly.

Figure 21-16: Result of executing a script (sample1.py)
# python sample1.py ls start file1 file2 rm start remove 'file1'? remove 'file2'? ping start PING 192.0.2.1 (192.0.2.1): 56 data bytes 64 bytes from 192.0.2.1: icmp_seq=0 ttl=63 time=0.377 ms 64 bytes from 192.0.2.1: icmp_seq=1 ttl=63 time=0.545 ms 64 bytes from 192.0.2.1: icmp_seq=2 ttl=63 time=1.349 ms 64 bytes from 192.0.2.1: icmp_seq=3 ttl=63 time=0.578 ms ----192.0.2.1 PING Statistics---- 4 packets transmitted, 4 packets received, 0.0% packet loss round-trip min/avg/max/stddev = 0.377/0.858/1.385/0.445 ms #

Figure 21-16: Result of executing a script (sample1.py)

# python sample1.py
ls start
file1 file2
 
rm start
remove 'file1'? remove 'file2'?
ping start
PING 192.0.2.1 (192.0.2.1): 56 data bytes
64 bytes from 192.0.2.1: icmp_seq=0 ttl=63 time=0.377 ms
64 bytes from 192.0.2.1: icmp_seq=1 ttl=63 time=0.545 ms
64 bytes from 192.0.2.1: icmp_seq=2 ttl=63 time=1.349 ms
64 bytes from 192.0.2.1: icmp_seq=3 ttl=63 time=0.578 ms
 
----192.0.2.1 PING Statistics----
4 packets transmitted, 4 packets received, 0.0% packet loss
round-trip min/avg/max/stddev = 0.377/0.858/1.385/0.445 ms
 
#

(b) Examples of Errors During Script Execution

The following is an example of specifying an invalid value for the command response timeout time.

Figure 21-17: Example of writing a script file (sample2.py)
# sample2.py # -- coding: utf-8 -- import extlib.commandline ..1 obj = extlib.commandline.CommandLine() ..2 # Command response timeout period (negative number is specified for time) print("ping start") dict_ret = obj.exec("ping 192.0.2.1", -3) ..3 print(dict_ret['strings']) ..4 obj.exit() ..5

Figure 21-17: Example of writing a script file (sample2.py)

# sample2.py
# -*- coding: utf-8 -*-
import extlib.commandline                                             ..1
obj = extlib.commandline.CommandLine()                                ..2
 
# Command response timeout period (negative number is specified for time)
print("ping start")
dict_ret = obj.exec("ping 192.0.2.1", -3)                             ..3
print(dict_ret['strings'])                                            ..4
 
obj.exit()                                                            ..5

Import the module.
Creates an instance of CommandLine.
In exec method, specify the timeout (negative) between the command to be executed and the command response.
Outputs the command execution result.
Ends the command execution status.

The script file sample2.py executes as follows: An error occurs because the value specified for the timeout period is incorrect.

Figure 21-18: Result of executing a script (sample2.py)
# python sample2.py ping start Traceback (most recent call last): File "sample2.py", line 7, in <module> dict_ret = obj.exec("ping 192.0.2.1", -3) File "/usr/local/lib/python3.2/site-packages/extlib/commandline.py", line 741, in exec CNST.ERR_TIMER_INVALID)) ValueError: The timer value is invalid. #

Figure 21-18: Result of executing a script (sample2.py)

# python sample2.py
ping start
Traceback (most recent call last):
  File "sample2.py", line 7, in <module>
    dict_ret = obj.exec("ping 192.0.2.1", -3)
  File "/usr/local/lib/python3.2/site-packages/extlib/commandline.py", line 741, in exec
    CNST.ERR_TIMER_INVALID))
ValueError: The timer value is invalid.
#

(c) Example of Command Execution Failure Exception

Here is an example of regenerating an instance when exec method encounters a command execution failure exception:

Figure 21-19: Example of writing a script file (sample3.py)
# sample3.py # -- coding: utf-8 -- import extlib.commandline ..1 obj = extlib.commandline.CommandLine() ..2 retry_cnt = 0 # Command without user response (ls) print("ls start") while retry_cnt < 3: try: dict_ret = obj.exec("ls") ..3 if dict_ret['result'] == extlib.commandline.OK: print(dict_ret['strings']) ..4 print("success!!") else: print("timeout.") break except extlib.commandline.ExecuteCommandError: ..5 obj.exit() ..6 obj = extlib.commandline.CommandLine() ..7 print("Regenerate the instance") retry_cnt = retry_cnt + 1 obj.exit() ..8

Figure 21-19: Example of writing a script file (sample3.py)

# sample3.py
# -*- coding: utf-8 -*-
import extlib.commandline                                             ..1
obj = extlib.commandline.CommandLine()                                ..2
 
retry_cnt = 0
 
# Command without user response (ls) 
print("ls start")
while retry_cnt < 3:
    try:
        dict_ret = obj.exec("ls")                                     ..3
        if dict_ret['result'] == extlib.commandline.OK:
            print(dict_ret['strings'])                                ..4
            print("success!!")
        else:
            print("timeout.")
        break
    except extlib.commandline.ExecuteCommandError:                    ..5
        obj.exit()                                                    ..6
        obj = extlib.commandline.CommandLine()                        ..7
        print("Regenerate the instance")
        retry_cnt = retry_cnt + 1
 
obj.exit()                                                            ..8

Import the module.
Creates an instance of CommandLine.
In exec method, specify the command to be executed (no user response).
Outputs the command execution result.
Captures exceptions for failed command executions in exec method.
Exits the command execution status.
Regenerate CommandLine instances.
Ends the command execution status.

The script file sample3.py executes as follows: Even if an exception occurs, the operation-command ls is executed correctly because the instance was regenerated.

Figure 21-20: Result of executing a script (sample3.py)
# python sample3.py ls start Regenerate the instance file1 file2 success!! #

(2) Instantiation

You cannot create more than one instance of CommandLine class for a single process. When you regenerate an instance, call exit method on the existing instance first.

(3) Executing Commands in exec Method

If you use exec method of commandline module to execute the command, the script-only user (username script) executes the corresponding command. The following tables show how to execute commands using exec method.

Table 21-16 Executing Commands Using the exec Method
Item	Description
Initial command input mode	User mode
Invalid command	For script-only users, setting changes made by executing the following operation commands are ignored: set exec-timeout set terminal pager The following configuration commands for script-only users are invalid: Logging-console Parameters for username Commands Exec-timeout Parameters for username Commands Terminal-pager Parameters for username Commands

(4) Command Approval

If command authorization is set for the Switch, command authorization is also applied to commands executed from scripts.

Commands executed from scripts are approved with the privilege of the username specified in username parameter of the configuration command aaa authorization commands script. If bypass parameter is specified, the command can be executed unconditionally without command authorization.

The following are special notes about command authorization:

Even if only aaa authorization commands script command is set, command authorization is not performed. Set these bits together with aaa authorization commands command.. However, command authorization by RADIUS server is not supported, so you need to configure command authorization by TACACS + server or locally.
When a command is executed by starting a script from an operation terminal connected by the console (RS232C), the command is approved according to the setting of aaa authorization commands console command.

When there is a aaa authorization commands console command-setting

It is subject to command approval. However, if bypass parameter is set, all commands can be executed without command authorization.

When there is no aaa authorization commands console command-setting

Command authorization is not performed. All commands can be executed.
If there is a aaa authorization commands command setting and the command authorization information (command class or command list) cannot be obtained, all commands cannot be executed. The following shows an example in which command authorization information cannot be acquired.
- There is no aaa authorization commands script command-setting.
- The specified username does not exist on TACACS + server or locally
- TACACS + server cannot be accessed
The command authorization information (command class or command list) is obtained when CommandLine class is instantiated.
When command authorization is set, the activation of the program by os.system() of Python standard library is also subject to the activation restriction. A program can be started only in the following cases:
- When there is no aaa authorization commands command-setting
- Aaa authorization commands command is set and bypass parameter of aaa authorization commands script command is set.
- When aaa authorization commands command is set, aaa authorization commands console command is not set, and the program is started by scripting started from the operation terminal connected by the console (RS232C)