How do you use posix_spawn to replace the deprecated 'system' to launch opendiff in Objective-C?

Question

This line of code:

system("/Applications/Xcode.app/Contents/Developer/usr/bin/opendiff /Users/LukeSkywalker/Documents/doc1.rtf /Users/LukeSkywalker/Documents/doc2.rtf");

gives me this warning:

'system' is deprecated: first deprecated in iOS 8.0 - Use posix_spawn APIs instead.

I've read a little bit about posix_spawn, but I can't figure out what an equivalent line of code using posix_spawn would look like.

Any help or links to samples would be appreciated.

Answer 1

Using posix_spawn(), to answer your question:

#include <spawn.h>
extern char **environ;

(...)

pid_t pid;
char *argv[] = {
    "/Applications/Xcode.app/Contents/Developer/usr/bin/opendiff",
    "/Users/LukeSkywalker/Documents/doc1.rtf",
    "/Users/LukeSkywalker/Documents/doc2.rtf",
    NULL
};

posix_spawn(&pid, argv[0], NULL, NULL, argv, environ);
waitpid(pid, NULL, 0);

Or, you could use NSTask:

NSTask *task = [[NSTask alloc] init];
task.launchPath = @"/Applications/Xcode.app/Contents/Developer/usr/bin/opendiff";
task.arguments = [NSArray arrayWithObjects:
                  @"/Users/LukeSkywalker/Documents/doc1.rtf",
                  @"/Users/LukeSkywalker/Documents/doc2.rtf",
                  nil];
[task launch];
[task waitUntilExit];

If you don't need it to be synchronous, just remove the call to waitpid() (make sure to call it somewhere else, or you'll end up with a zombie process until your app exits) or [task waitUntilExit].