Art Del Cueto wants the wall, but he also needs a paycheck.

Border Patrol agents like Del Cueto — in the crossfire of the government shutdown fight over President Donald Trump’s demand for a border wall — are preparing to work without pay when the government shuts down tonight.

“It’s nerve-racking,” said Del Cueto, who is a vice president of the National Border Patrol Council, a union, and works in Arizona. “It sucks, to be honest.”

Federal bureaucrats have become adept at blunting the effect of shutdowns on federal services, and the two shutdowns this year — a 69-hour interruption in January followed by a nine-hour funding lapse in February — had a negligible impact.

But this month’s bitter and unpredictable fight over Trump’s insistence that Congress immediately allocate $5 billion for a wall on the Mexican border could be different, with the president today predicting a protracted shutdown unless he got his way.

As in previous government shutdowns, it would not affect core governmental functions like the Postal Service, the military, the Department of Veterans Affairs and entitlement programs, including Social Security, Medicaid, Medicare and food stamps.

But about 380,000 workers at nine of 15 Cabinet-level departments would be sent home and would not be paid for the time off. Another 420,000 deemed too essential to be furloughed would be forced, like the Border Patrol officers, to work without pay. After past shutdowns, such workers have been reimbursed later.

The Departments of Agriculture, Commerce, Homeland Security, Housing and Urban Development, Interior — which includes national parks — Justice, State, Transportation and Treasury would all be affected. NASA would also be hit.

Here is a rundown on how a shutdown would affect federal departments:

Department of Homeland Security

The department, which handles border security to airport screening to deterrence of terrorist attacks against the United States, would largely remain open.

The 60,000 employees at Customs and Border Protection would be forced to work without pay, as would airline screeners and security officers at the Transportation Security Administration, so holiday air travel and security operations would not be disrupted.

Special agents at the Secret Service, who guard the president and other officials, would continue to work, as would emergency management personnel.

Thousands of administrators and managers at the department, including many in the Coast Guard, would be furloughed, depriving workers who have to remain at their posts of support. The potential for a holiday shutdown was adding to the stress of already difficult work — with leave for many workers being canceled.

“I want that budget for the wall,” Del Cueto said. “I also have skin in the game. I’m not getting paid, and I’m defending our borders.”

— Ron Nixon and Mitchell Ferman

Interior Department

The most visible impact of a shutdown would be in national parks and forests, with 80 percent of employees at the National Park Service facing immediate furloughs.

The timing, however, would be helpful. Many of the nation’s most heavily trafficked parks are either closed during the winter or see major drop-offs in visits, and in some instances state officials are planning to step unto the breach.

Most parks, including the National Mall, would remain open without staff members to provide guidance or support, according to the department’s 2018 contingency plan. The Smithsonian museums have the funding to remain open, its staff said in a tweet today.

Gov. Doug Ducey of Arizona announced today that the state would do everything it could to keep the Grand Canyon from closing, and would pick up the tab for shuttles and public restrooms.

David Freireich, a spokesman for Aramark, which operates hotels and restaurants inside Yosemite National Park in California, predicted “business as usual.”

In the Pacific Northwest, backcountry skiers at places like North Cascades National Park, northeast of Seattle, could find limited access to some areas and services.

Environmental groups have pointed out that shutdowns have traditionally been hard on local ecosystems, leading to trash pileups and visitor misbehavior. During January’s shutdown, a poacher killed a pregnant elk inside Zion National Park, apparently taking advantage of a lack of park security. At Yellowstone, visitors drove snowmobiles into prohibited areas.

— Thomas Fuller, Julie Turkewitz and Kirk Johnson

Treasury Department

Nine out of 10 employees at the IRS would be furloughed, temporarily curtailing audits and other enforcement actions, but also shuttering services intended to assist taxpayers.

Department employees deemed essential are those responsible for safeguarding federal property and administering Treasury accounts, and employees directly involved in carrying out the shutdown, according to contingency plans filed last month.

State Department

The issuing of passports and other consular functions are funded by multiyear spending bills and are expected to continue during a shutdown, though some may be curtailed if the buildings that house them are shuttered because of a lapse in funding, according to department guidelines issued this year.

International travelers who suddenly realize that their passport has expired, or who are looking to get a new one, could be out of luck. Visa and passport services would continue “as long as there are sufficient fees to support operations,” a department spokesman said.

— Emily Cochrane

Agriculture Department

The department would continue to inspect meat, poultry and egg products, including those being certified for export, according to Kevin Shea, administrator for the Animal and Plant Health Inspection Service.

The Food Safety and Inspection Service, which houses the agency’s epidemiology experts, would continue its role in monitoring food products and would be prepared to conduct any emergency investigations into food-borne disease outbreaks.

Programs that comprise the nutrition safety net — including food stamps, children’s subsidized meals and the Special Supplemental Nutrition Program for Women, Infants and Children, known as WIC — would remain open.

— Emily Baumgaertner

Justice Department

The department would largely remain at work because the vast majority of its functions involve “the safety of human life and the protection of property,” the legal benchmark for exemption.

According to the department’s shutdown plan, 85 percent, or 95,339, of its 113,546 employees would work without pay.

Transportation Department

About 34,600 of the department’s 55,100 employees would continue working during a shutdown. Railroad safety inspectors, air traffic controllers and most Federal Highway Administration employees would remain on the job, and roadside truck inspections would also proceed, according to the department’s contingency plan, published in January.

Some functions would be temporarily stopped, including certification of new aircraft, air traffic controller training and the issuance of new pilot licenses.

— Emily Baumgaertner

Department of Housing and Urban Development

About 95 percent of the department’s employees would be furloughed, halting fair housing enforcement, housing quality inspections and the issuance of new development grants.

The Federal Housing Administration would be likely to see significant delays in loan processing and approvals, meaning new homebuyers may be placed on standby, and payments to roughly 3,000 public housing agencies would be delayed.

— Emily Cochrane

Commerce Department

About 41,000 people in the department, or 86 percent, would be furloughed, bringing the agency’s work, including investigations and enforcement actions, to a nearly complete halt.

NASA

An estimated 96 percent of staff members at the space agency would be furloughed, according to the agency’s 2018 shutdown plan.

In a statement,a NASA spokeswoman, Megan Powers, said: “In previous shutdowns, we have maintained personnel to support the International Space Station and its crew, and currently operating space missions, such as satellites, landers, rovers, to ensure they’re safe and secure.”