Understanding Extension Functions in Junos OS Automation Scripts

Junos OS provides automation scripting tools, including extension functions and named templates, that can be used in commit, op, event, and SNMP scripts to more easily accomplish scripting tasks on devices running Junos OS. The libraries provide logic, data manipulation, input and output, and utility functions and enable you to perform operations that are difficult or impossible to perform in XPath. Table 1 summarizes the Juniper extension functions.

To use the extension functions, Python automation scripts must import the jcs module, and SLAX and XSLT scripts must declare the appropriate namespace URI in the style sheet declaration. A function in the jcs namespace is defined in the namespace URI http://xml.juniper.net/junos/commit-scripts/1.0, and a function in the slax namespace is defined in the namespace URI http://xml.libslax.org/slax .

Functions using the slax namespace are supported starting in Junos OS Release 12.2. Scripts using Junos OS-independent extension functions that existed in earlier releases in the jcs namespace can use either the jcs or the slax namespace starting in Junos OS Release 12.2. However, to use any of these functions in earlier Junos OS releases, scripts must use the jcs namespace URI.

The SLAX script version statement determines which functions can be used in that script. In order to use a function that was introduced in a specific SLAX version, the value of the script version statement must be equal to or greater than the version in which the function was introduced. For example, functions introduced in version 1.1 of the SLAX language cannot be used in a SLAX script that has a "version 1.0" statement.

Note:

SLAX scripts can also use additional functions from the libslax default extension libraries. For more information, see libslax Default Extension Libraries: bit, curl, db, os, and xutil.

Python automation scripts only support a subset of the extension functions. For many of the unsupported functions, you can use standard Python libraries to achieve the same functionality.

Table 1: Extension Functions for Use in Automation Scripts
Function	Name-spaces	SLAX Version	Type	Description	Support in Python Scripts
`base64-decode()`	slax	1.1	Data manipulation	Decode BASE64 encoded data and return a string.	–
`base64-encode()`	slax	1.1	Data manipulation	Encode a string of data in the BASE64 encoding format.	–
`break-lines()`	jcs, slax	1.0	Data manipulation	Break a simple element into multiple elements, delimited by newlines.	–
`close()`	jcs	1.0	Utility	Close a previously opened connection handle.	–
`dampen()`	jcs, slax	1.0	Utility	Prevent the same operation from being repeatedly executed within a script.	Y
`document()`	slax	1.1	Input/output control	Read data from a file or URL and return a string.	–
`emit_change()`	–	–	Utility	Generate a persistent or transient change to the configuration in a commit script.	Y
`emit_error()`	–	–	Input/output control	Generate an error message on the console.	Y
`emit_snmp_attributes()`	–	–	Input/output control	Return information for the requested MIB object from an SNMP script.	Y
`emit_warning()`	–	–	Input/output control	Generate a warning message on the console.	Y
`empty()`	jcs, slax	1.0	Logic	Evaluate a node set or string argument to determine if it is an empty value.	–
`evaluate()`	slax	1.1	Input/output control	Evaluate a SLAX expression and return the result.	–
`execute()`	jcs	1.0	Utility	Execute a remote procedure call (RPC) within the context of a specified connection handle.	–
`first-of()`	jcs, slax	1.0	Logic	Return the first nonempty (non-null) item in a list, If all objects in the list are empty, the default expression is returned.	–
`get-command()`	jcs, slax	1.1	Input/output control	Prompt the user for command input and return the input as a string.	–
`get-hello()`	jcs	1.0	Utility	Return the session ID and the capabilities of the NETCONF server during a NETCONF session.	–
`get-input()` (XSLT/SLAX) `get_input() (Python)`	jcs, slax	1.0	Input/output control	Invoke a CLI prompt and wait for user input. If the script is run non-interactively, the function returns an empty value. This function cannot be used with event scripts.	Y
`get-protocol()`	jcs	1.0	Utility	Return the session protocol associated with the connection handle.	–
`get-secret()` (XSLT/SLAX) `get_secret()` (Python)	jcs, slax	1.0	Input/output control	Invoke a CLI prompt and wait for user input. The input is not echoed back to the user.	Y
`get_snmp_action()`	–	–	Input/output control	Retrieve the action value passed to the SNMP script.	Y
`get_snmp_oid()`	–	–	Input/output control	Retrieve the OID value passed to the SNMP script.	Y
`hostname()`	jcs	1.0	Utility	Return the fully qualified domain name associated with a given IPv4 or IPv6 address, provided the DNS server is configured on the device.	Y
`invoke()`	jcs	1.0	Utility	Invoke an RPC on a local device running Junos OS.	–
`open()`	jcs	1.0	Utility	Return a connection handle that can be used to execute RPCs.	–
`output()`	jcs, slax	1.0	Input/output control	Generate unformatted output text that is immediately sent to the CLI session.	Y
`parse-ip()`	jcs	1.0	Data manipulation	Parse an IPv4 or IPv6 address and return the host IP address, protocol family, prefix length, network address, and network mask.	Y
`printf()`	jcs, slax	1.0	Input/output control	Generate formatted output text. Most standard `printf` formats are supported, in addition to some Junos OS-specific formats. The function returns a formatted string but does not print it on call.	Y
`progress()`	jcs, slax	1.0	Input/output control	Issue a progress message containing the single argument immediately to the CLI session provided that the `detail` flag was specified when the script was invoked.	Y
`regex()`	jcs, slax	1.0	Data manipulation	Evaluate a regular expression against a given string argument and return any matches.	–
`set_routing_instance()`	-	-	Utility	Program the protocol software (TCP/UDP) to use nondefault routing instances.	Y
`sleep()`	jcs, slax	1.0	Utility	Cause the script to sleep for a specified time.	–
`split()`	jcs, slax	1.0	Data manipulation	Split a string into an array of substrings delimited by a regular expression pattern.	–
`sysctl()`	jcs, slax	1.0	Utility	Return the value of the given `sysctl` value as a string or an integer.	Y
`syslog()`	jcs, slax	1.0	Input/output control	Log messages with the specified priority to the system log file.	Y
`trace()`	jcs, slax	1.0	Input/output control	Issue a trace message, which is sent to the trace file.	Y

Understanding Extension Functions in Junos OS Automation Scripts

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