He’s been shot at and knifed, but the way to really get on John Shaft’s bad side is to dress like crap.

The legendary private eye personifies street cool with an impressive array of hard-boiled jackets, tightfitting trousers and fly headgear. It’s no exaggeration to say he’s become one of cinema’s most famous fashion plates.

Over the years, designers including Celine and Jason Wu have showcased looks nodding to the “bad motherf - - ker.”

“The way he looked really resonated with the people who watched the film and subsequently analyzed it,” Joe Aulisi, the costume designer for the original 1971 film starring Richard Roundtree, tells The Post.

Now Shaft is back, and with him a semi-truck’s worth of leather duster jackets that only the most baadassss among us could hope to pull off.

Samuel L. Jackson is the titular detective in Friday’s “Shaft,” teaming with his father (Roundtree) and son (Jessie T. Usher) to tackle a case set in Harlem’s underworld.

This time around, Shaft looks a little different from past installments, in part to differentiate Jackson from his other popular leather-clad character.

“With Sam appearing in all the Marvel movies, we did not want to harken back to Nick Fury,” “Shaft” costume designer Olivia Miles tells The Post. “So no black leather. We came up with our own color palette, which was deep and rich and looked good against the gritty [NYC backdrop].”

He’s still got the leather jackets though — he wears some 12 different ones, including calf-length numbers and blazers throughout the film. It’s just that they come in different shades. Almost all were custom-made, although Miles did buy some off the rack from Brioni and John Varvatos.

Jackson had input into his character’s wardrobe.

“He knows fashion and he knows what looks good and what silhouettes flatter,” Miles says.

Shaft Jr. evidently did not inherit his father’s sense of style, and Jackson’s character takes fashion potshots, as he’s done in past movies.

“You come in here with your skinny jeans and your plaid, button-down Gap shirt,” he scoffs at Junior in the film.

But that disconnect was planned. Miles wanted to give each generation of Shaft his own fashion identity.

While Jackson had a more tailored look, Roundtree got a bit of a throwback to the decade of the original “Shaft.”

For that film, Aulisi took inspiration from another series.

“The James Bond movies had just started a few years earlier, so Shaft was supposed to look as great as that but more of the world that he comes from,” Aulisi says, stressing the movie was never meant to be a “fashion piece.”

The clothes were all custom-made, and his trademark leather jackets came about because director Gordon Parks, the late famous still photographer, knew the material would look good on film. Leather also conveyed toughness.

Roundtree, who once worked as a clothes salesman and model, made the outfits look good. The look was so popular, a line of Shaft clothing and belt buckles launched.

In the new “Shaft,” Roundtree dons mod, hip-length jackets, Cuban heel boots and Levi’s Sta-Prest slacks that were popular decades ago.

Shaft Jr., however, probably had little disposable income and was dressed in off-the-rack duds from fashion chains such as H&M and Zara.

If this movie brings Shaft back into fashion again, the average Joe or Jane (the look is unisex) can take part. Miles suggests borrowing the character’s basics: pairing a turtleneck sweater and a tailored pair of trousers with a leather duster.

“This is a timeless silhouette,” she says.

You’re damn right.

Click Here: cheap kanken backpack