Many network devices provide two commands to retrieve specific information: the first command returns a summarized output in tabular format,

Many network devices provide two commands to retrieve specific information: the first command returns a summarized output in tabular format, while the second command provides a more detailed view, typically in a non-tabular format where each entry is separated into a specific section.

Although the tabular format is more human-readable, non-tabular text is significantly easier for a machine to interpret.

Let’s look at an example: the show interfaces command displays detailed information about the interfaces configured on a switch.

The first step is to identify the pieces of information we’re interested in, each of which must be associated with a RegEx. Here are a few examples:

• Interface, which is mandatory and serves as the key: \w+/\d+/\d+
• Bandwidth, which is a string delimited by a comma: [^,]+
• Description, which is a generic string ending at the end of the line: .+
• Line status, which is one of several possible strings: up|down|administratively down
• MAC address, which consists of three hexadecimal sequences separated by dots: ([0-9a-f.]{4}.){2}[0-9a-f]{4}
• MTU, which is a number: \d+
• Protocol status, which is one of several possible strings: up|down
• Interface type, which is a string delimited by a comma: [^,]+

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