我应该使用什么函数来转义C中的shell命令参数的字符串？
我有一个字符串：
This is a string with () characters
这将是错误：
echo This is a string with () characters
这些都可以：
echo "This is a string with () characters"
echo This is a string with \(\) characters
C中是否有预定义函数将＃2转换为＃3
答案 0 :(得分：7)
用'替换'\''的所有实例，然后将整个字符串括在单引号（'）中是一种安全的方法。这甚至适用于嵌入式换行。另一种方法是在每个字符之前插入\，除了那时你必须对换行进行一些特殊的处理，因为\后面跟一个新行被shell忽略，而不是作为文字换行。您必须使用'（单引号）包围换行符。
答案 1 :(得分：2)
答案 2 :(得分：1)
没有预定义，以及哪些字符需要转义取决于你的shell。查看shell的文档，并用\ X替换每个X.如果你所包围的字符串包含“。
，则使用双引号”将需要相同的处理另请注意，如果您打算封装更复杂的表达式（例如，任何与';'复合的表达式），这将变得更加复杂
答案 3 :(得分：1)
C不是我选择的语言，但这就是我想出的结果（我自己必须回答同样的问题）。
#include <stdio.h> // sprintf
#include <stdlib.h> // malloc
#include <string.h> // strlen
char* escapeshellarg(char* str) {
char *escStr;
int i,
count = strlen(str),
ptr_size = count+3;
escStr = (char *) calloc(ptr_size, sizeof(char));
if (escStr == NULL) {
return NULL;
}
sprintf(escStr, "'");
for(i=0; i<count; i++) {
if (str[i] == '\'') {
ptr_size += 3;
escStr = (char *) realloc(escStr,ptr_size * sizeof(char)));
if (escStr == NULL) {
return NULL;
}
sprintf(escStr, "%s'\\''", escStr);
} else {
sprintf(escStr, "%s%c", escStr, str[i]);
}
}
sprintf(escStr, "%s%c", escStr, '\'');
return escStr;
}
给定escape'this'，它会输出'escape'\''this'\'''，然后可以传递给echo。
$ echo 'escape'\''this'\'''
escape'this'
答案 4 :(得分：0)
你的第二个版本很简单，不是吗？
printf("\"%s\"", your string);
答案 5 :(得分：0)
将每个单引号class ViewController: UIViewController, NSFetchedResultsControllerDelegate {
public var cities: [City] = []
private lazy var citiesResultsController: NSFetchedResultsController<City> = {
let request: NSFetchRequest<City> = City.fetchRequest()
request.sortDescriptors = [NSSortDescriptor(key: "creationDate", ascending: true)]
let controller = NSFetchedResultsController(fetchRequest: request, managedObjectContext: AppDelegate.managedObjectContext, sectionNameKeyPath: nil, cacheName: nil)
controller.delegate = self
return controller
}()
public var roads: [Road] = []
private lazy var roadsResultsController: NSFetchedResultsController<Road> = {
let request: NSFetchRequest<Road> = Road.fetchRequest()
request.sortDescriptors = [NSSortDescriptor(key: "creationDate", ascending: true)]
let controller = NSFetchedResultsController(fetchRequest: request, managedObjectContext: AppDelegate.managedObjectContext, sectionNameKeyPath: nil, cacheName: nil)
controller.delegate = self
return controller
}()
func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChangeContentWith diff: CollectionDifference<NSManagedObjectID>) {
if controller === citiesResultsController {
for change in diff {
switch change {
case .insert(offset: let newPosition, element: _, associatedWith: let oldPosition):
if let oldPosition = oldPosition {
// was moved
// HERE IT CRASHES
let city = cities.remove(at: oldPosition)
cities.insert(city, at: newPosition)
} else {
// was inserted
let city = citiesResultsController.object(at: IndexPath(item: newPosition, section: 0))
cities.insert(city, at: newPosition)
}
case .remove(offset: let position, element: _, associatedWith: let associatedWith):
if associatedWith == nil {
_ = cities.remove(at: position)
}
}
}
} else {
for change in diff {
switch change {
case .insert(offset: let newPosition, element: _, associatedWith: let oldPosition):
if let oldPosition = oldPosition {
// was moved
let road = roads.remove(at: oldPosition)
roads.insert(road, at: newPosition)
} else {
// was inserted
let road = roadsResultsController.object(at: IndexPath(item: newPosition, section: 0))
roads.insert(road, at: newPosition)
}
case .remove(offset: let position, element: _, associatedWith: let associatedWith):
if associatedWith == nil {
_ = roads.remove(at: position)
}
}
}
}
}
override func viewDidLoad() {
super.viewDidLoad()
try? citiesResultsController.performFetch()
cities = citiesResultsController.fetchedObjects ?? []
try? roadsResultsController.performFetch()
roads = roadsResultsController.fetchedObjects ?? []
DispatchQueue.main.asyncAfter(deadline: .now() + .seconds(5)) {
print("Now")
AppDelegate.managedObjectContext.delete(AppDelegate.cityA)
try! AppDelegate.managedObjectContext.save()
}
}
}
替换为//
// AppDelegate.swift
// TestProject
//
// Created by Dennis Müller on 23.09.19.
// Copyright © 2019 Dennis Müller. All rights reserved.
//
import UIKit
import CoreData
@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
public static var managedObjectContext: NSManagedObjectContext {
return (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
}
public static var cityA: City!
func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
// Override point for customization after application launch.
if !UserDefaults.standard.bool(forKey: "setup") {
UserDefaults.standard.set(true, forKey: "setup")
let cityA = City(context: persistentContainer.viewContext)
cityA.name = "cityA"
cityA.creationDate = Date()
let cityB = City(context: persistentContainer.viewContext)
cityB.name = "cityB"
cityB.creationDate = Date()
let road = Road(context: persistentContainer.viewContext)
road.creationDate = Date()
road.addToCities(cityA)
road.addToCities(cityB)
saveContext()
}
let request: NSFetchRequest<City> = City.fetchRequest()
request.predicate = NSPredicate(format: "name == %@", "cityA")
AppDelegate.cityA = try! persistentContainer.viewContext.fetch(request).first!
return true
}
// MARK: UISceneSession Lifecycle
func application(_ application: UIApplication, configurationForConnecting connectingSceneSession: UISceneSession, options: UIScene.ConnectionOptions) -> UISceneConfiguration {
// Called when a new scene session is being created.
// Use this method to select a configuration to create the new scene with.
return UISceneConfiguration(name: "Default Configuration", sessionRole: connectingSceneSession.role)
}
func application(_ application: UIApplication, didDiscardSceneSessions sceneSessions: Set<UISceneSession>) {
// Called when the user discards a scene session.
// If any sessions were discarded while the application was not running, this will be called shortly after application:didFinishLaunchingWithOptions.
// Use this method to release any resources that were specific to the discarded scenes, as they will not return.
}
// MARK: - Core Data stack
lazy var persistentContainer: NSPersistentContainer = {
/*
The persistent container for the application. This implementation
creates and returns a container, having loaded the store for the
application to it. This property is optional since there are legitimate
error conditions that could cause the creation of the store to fail.
*/
let container = NSPersistentContainer(name: "TestProject")
container.loadPersistentStores(completionHandler: { (storeDescription, error) in
if let error = error as NSError? {
// Replace this implementation with code to handle the error appropriately.
// fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
/*
Typical reasons for an error here include:
* The parent directory does not exist, cannot be created, or disallows writing.
* The persistent store is not accessible, due to permissions or data protection when the device is locked.
* The device is out of space.
* The store could not be migrated to the current model version.
Check the error message to determine what the actual problem was.
*/
fatalError("Unresolved error \(error), \(error.userInfo)")
}
})
return container
}()
// MARK: - Core Data Saving support
func saveContext () {
let context = persistentContainer.viewContext
if context.hasChanges {
do {
try context.save()
} catch {
// Replace this implementation with code to handle the error appropriately.
// fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
let nserror = error as NSError
fatalError("Unresolved error \(nserror), \(nserror.userInfo)")
}
}
}
}
，然后将结果字符串括在单引号'之间：
'\''