Matthew Kenneth James Auld was heavily intoxicated near the Florey shops in March when the aggravated robbery occurred.

Auld confronted a woman on a footpath near the shops, brandishing a knife and demanding money.

The woman broke into tears, fearing she would be stabbed.

She gave Auld a $5 note, and he then walked to the Florey shops, accompanied by two women.

He flashed his knife at a number of people, demanding cigarettes.

A security guard kept Auld calm and gave him cigarettes until police arrived.

A police informant told the court earlier this year Auld was slurring his words, was unsteady on his feet and seemed intoxicated while one of his female companions was carrying a ''nearly empty'' bottle of vodka.

The court heard the woman victim of the robbery had been ''frozen with fear'', and ran home in tears soon after.

She said the robbery left her so traumatised that she was unable to walk down the footpath that she had used regularly for four years. She said she feared someone would be lurking in the underpass.

The court heard the woman was ''sad and angry part of my confidence has been replaced by fear''.

In handing down her sentence on Friday, Justice Hilary Penfold said she was not convinced Auld was genuinely ready to change his ways. She said a sentence of imprisonment was necessary as a deterrent.

The court heard the crime also breached Auld's good behaviour order for a burglary offence in 2011. Justice Penfold sentenced Auld to two years and eight months in prison, with a non-parole period of 18 months.

She told Auld, who is aged in his late 20s, that he was ''too old to keep making excuses'' for himself.

Auld has been in prison since late March, making him eligible for parole in September 2013.