Karwan Kamal left his victim scarred for life after the attack outside the Mo Salah takeaway shop on Stanley Road, Harehills, Leeds Crown Court was told.
The man, who was bleeding heavily, suffered a 20cm long cut across his jaw and neck and down to his collarbone
He was taken to Leeds General Infirmary where the wound was stitched.
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A judge handed 46-year-old Kamal, of Lincoln Green Road, Burmantofts, an extended sentence of more than nine years.
Mehran Nassiri, prosecuting, said Kamal arrived at the takeaway at around 11pm on Saturday September 14 2019 just as the complainant was locking the door and closing the shop.
Mr Nassiri said the takeaway worker was taking the bin out to the backyard at the shop when Kamal appeared and started to shout abuse before grabbing hold of him.
The court heard there was a struggle and Kamal threatened to stab the man in the eye.
He then took a knife out of his pocket and slashed his neck and throat.
Kamal then dropped the knife and ran off towards St James's Hospital.
Three days later, the victim called police after spotting Kamal on a bus and he was arrested.
Kamal, who told police he was drunk at the time of the offence, admitted wounding with intent and possessing a bladed article.
The court heard he has six previous convictions for 12 offences, including possessing a bladed article and assault.
A Kurdish interpreter relayed the court proceedings to Kamal.
Chloe Hudson, mitigating, said: "He has a long standing history of mental disorder."
Judge Christopher Batty said: "You were angry that you could not get into the premises and buy food."
Judge Batty added: "It's simply good fortune that he was not more seriously injured. He could have died."
Judge Batty said Kamal suffers from paranoid schizophrenia.
The court heard a psychiatrist who examined Kamal concluded he poses a high risk of committing further offences.
Judge Batty imposed an extended sentence of nine-years-and-four-months.
Kamal must serve a prison sentence of five-years-and-four-months plus a four-year extended licence.