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做越狱应用和插件开发，经常会调用 system 去执行系统命令，早在 Xcode 7，使用 system 函数提示警告：
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'system' is deprecated: first deprecated in iOS 8.0 - Use posix_spawn APIs installd
只是警告，还是可以正常编译和使用，但是升级到 Xcode 9，system 函数就从 SDK 中移除了，不能再使用了，提示：
'system' is unavailable: not available on iOS
替代的方法一般有三种，第一种是使用 posix_spawn，代码如下：
pid_t pid;
char *argv[] = {
"/bin/ls", //path
"-al", //parameter1
"/", //parameter2
NULL
};
posix_spawn(&pid, argv[0], NULL, NULL, argv, NULL);
printf("pid=%d,child pid = %d\n",getpid(),pid);
int stat;
waitpid(pid,&stat,0);
printf("stat is %d\n",stat);第二种是使用 NSTask，代码如下：
NSTask *task = [[NSTask alloc] init]; task.launchPath = @"/bin/ls"; task.arguments = [NSArray arrayWithObjects: @"-al", @"/", nil]; [task launch]; [task waitUntilExit];
NSTask.h 头文件信息如下：
#import@class NSString, NSArray, NSDictionary; @interface NSTask : NSObject // Create an NSTask which can be run at a later time // An NSTask can only be run once. Subsequent attempts to // run an NSTask will raise. // Upon task death a notification will be sent // { Name = NSTaskDidTerminateNotification; object = task; } // - (instancetype)init; // set parameters // these methods can only be done before a launch // if not set, use current // if not set, use current // set standard I/O channels; may be either an NSFileHandle or an NSPipe - (void)setStandardInput:(id)input; - (void)setStandardOutput:(id)output; - (void)setStandardError:(id)error; // get parameters @property (NS_NONATOMIC_IOSONLY, copy) NSString *launchPath; @property (NS_NONATOMIC_IOSONLY, copy) NSArray *arguments; @property (NS_NONATOMIC_IOSONLY, copy) NSDictionary *environment; @property (NS_NONATOMIC_IOSONLY, copy) NSString *currentDirectoryPath; // get standard I/O channels; could be either an NSFileHandle or an NSPipe - (id)standardInput; - (id)standardOutput; - (id)standardError; // actions - (void)launch; - (void)interrupt; // Not always possible. Sends SIGINT. - (void)terminate; // Not always possible. Sends SIGTERM. @property (NS_NONATOMIC_IOSONLY, readonly) BOOL suspend; @property (NS_NONATOMIC_IOSONLY, readonly) BOOL resume; // status @property (NS_NONATOMIC_IOSONLY, readonly) int processIdentifier; @property (NS_NONATOMIC_IOSONLY, getter=isRunning, readonly) BOOL running; @property (NS_NONATOMIC_IOSONLY, readonly) int terminationStatus; @end @interface NSTask (NSTaskConveniences) + (NSTask *)launchedTaskWithLaunchPath:(NSString *)path arguments:(NSArray *)arguments; // convenience; create and launch - (void)waitUntilExit; // poll the runLoop in defaultMode until task completes @end FOUNDATION_EXPORT NSString * const NSTaskDidTerminateNotification;
如果非要调用 system 函数不可，那就使用第三种方法，找到 system 函数地址直接调用，方法参见: 动态调用函数，具体代码如下：
typedef int (*my_system) (const char *str);
int call_system(const char *str){
//动态库路径
char *dylib_path = "/usr/lib/libSystem.dylib";
//打开动态库
void *handle = dlopen(dylib_path, RTLD_GLOBAL | RTLD_NOW);
if (handle == NULL) {
//打开动态库出错
fprintf(stderr, "%s\n", dlerror());
} else {
//获取 system 地址
my_system system = dlsym(handle, "system");
//地址获取成功则调用
if (system) {
int ret = system(str);
return ret;
}
dlclose(handle); //关闭句柄
}
return -1;
}这样 call_system 函数就相当于 system 的功能了，替换即可。
原文地址：https://www.exchen.net/ios-hacker-system-%E5%87%BD%E6%95%B0%E8%A2%AB%E5%BA%9F%E9%99%A4%E7%9A%84%E6%9B%BF%E4%BB%A3%E6%96%B9%E6%B3%95.html
