Mathew McKenna robbed a teenager at knifepoint, wounded a woman in the face and slashed a 65-year-old pensioner.
McKenna,44 has previous convictions for robbery, serious assault and carrying a knife. The judge ordered that he should be kept under supervision for a further four years.
Unemployed McKenna, of Croftwood Avenue, Glasgow, McKenna attacked and robbed his first victim, 19-year-old Jamie Massot, as he headed home to the South Side at Glasgow Bridge on January 26 this year.
After midnight McKenna walked into the Empire Bar at Saltmarket but was told last orders had been called.
He walked back out and cook Caroline Weaver, 40 who was standing outside also told him the pub was closed. McKenna struck her to the face with a knife.
A male passerby punched McKenna in the face, but he then lashed out and struck retired Joseph McPhelim. The passerby then punched McKenna again and he fell to the ground.
Mr McPhelim and Ms Weaver were taken to hospital. Mr McPhelim had 20 stitches put in his ear and scalp and will be will be scarred for life. Ms Weaver had a cut above her right eyebrow glued.
McKenna later pled guilty to assaulting and robbing Mr Massot, assaulting Ms Weaver to her injury and assaulting Mr McPhelim to his severe injury and permanent disfigurement.
Defence solicitor advocate Jim Stephenson said McKenna had taken steps to deal with a drug problem.