Execute a terminal command from a Cocoa app

2018-12-31 08:22发布

How can I execute a terminal command (like grep) from my Objective-C Cocoa application?

11条回答
宁负流年不负卿
2楼-- · 2018-12-31 09:01

There is also good old POSIX system("echo -en '\007'");

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谁念西风独自凉
3楼-- · 2018-12-31 09:05

Custos Mortem said:

I'm surprised no one really got into blocking/non-blocking call issues

For blocking/non-blocking call issues regarding NSTask read below:

asynctask.m -- sample code that shows how to implement asynchronous stdin, stdout & stderr streams for processing data with NSTask

Source code of asynctask.m is available at GitHub.

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后来的你喜欢了谁
4楼-- · 2018-12-31 09:13

Here's how to do it in Swift

Changes for Swift 3.0:

  • NSPipe has been renamed Pipe

  • NSTask has been renamed Process


This is based on inkit's Objective-C answer above. He wrote it as a category on NSString — For Swift, it becomes an extension of String.

extension  String.runAsCommand()  ->  String

extension String {
    func runAsCommand() -> String {
        let pipe = Pipe()
        let task = Process()
        task.launchPath = "/bin/sh"
        task.arguments = ["-c", String(format:"%@", self)]
        task.standardOutput = pipe
        let file = pipe.fileHandleForReading
        task.launch()
        if let result = NSString(data: file.readDataToEndOfFile(), encoding: String.Encoding.utf8.rawValue) {
            return result as String
        }
        else {
            return "--- Error running command - Unable to initialize string from file data ---"
        }
    }
}

Usage:

let input = "echo hello"
let output = input.runAsCommand()
print(output)                        // prints "hello"

    or just:

print("echo hello".runAsCommand())   // prints "hello" 

Example:

@IBAction func toggleFinderShowAllFiles(_ sender: AnyObject) {

    var newSetting = ""
    let readDefaultsCommand = "defaults read com.apple.finder AppleShowAllFiles"

    let oldSetting = readDefaultsCommand.runAsCommand()

    // Note: the Command results are terminated with a newline character

    if (oldSetting == "0\n") { newSetting = "1" }
    else { newSetting = "0" }

    let writeDefaultsCommand = "defaults write com.apple.finder AppleShowAllFiles \(newSetting) ; killall Finder"

    _ = writeDefaultsCommand.runAsCommand()

}

Note the Process result as read from the Pipe is an NSString object. It might be an error string and it can also be an empty string, but it should always be an NSString.

So, as long as it's not nil, the result can cast as a Swift String and returned.

If for some reason no NSString at all can be initialized from the file data, the function returns an error message. The function could have been written to return an optional String?, but that would be awkward to use and wouldn't serve a useful purpose because it's so unlikely for this to occur.

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骚的不知所云
5楼-- · 2018-12-31 09:18

I wrote this "C" function, because NSTask is obnoxious..

NSString * runCommand(NSString* c) {

    NSString* outP; FILE *read_fp;  char buffer[BUFSIZ + 1];
    int chars_read; memset(buffer, '\0', sizeof(buffer));
    read_fp = popen(c.UTF8String, "r");
    if (read_fp != NULL) {
        chars_read = fread(buffer, sizeof(char), BUFSIZ, read_fp);
        if (chars_read > 0) outP = $UTF8(buffer);
        pclose(read_fp);
    }   
    return outP;
}

NSLog(@"%@", runCommand(@"ls -la /")); 

total 16751
drwxrwxr-x+ 60 root        wheel     2108 May 24 15:19 .
drwxrwxr-x+ 60 root        wheel     2108 May 24 15:19 ..
…

oh, and for the sake of being complete / unambiguous…

#define $UTF8(A) ((NSString*)[NSS stringWithUTF8String:A])

Years later, C is still a bewildering mess, to me.. and with little faith in my ability to correct my gross shortcomings above - the only olive branch I offer is a rezhuzhed version of @inket's answer that is barest of bones, for my fellow purists / verbosity-haters...

id _system(id cmd) { 
   return !cmd ? nil : ({ NSPipe* pipe; NSTask * task;
  [task = NSTask.new setValuesForKeysWithDictionary: 
    @{ @"launchPath" : @"/bin/sh", 
        @"arguments" : @[@"-c", cmd],
   @"standardOutput" : pipe = NSPipe.pipe}]; [task launch];
  [NSString.alloc initWithData:
     pipe.fileHandleForReading.readDataToEndOfFile
                      encoding:NSUTF8StringEncoding]; });
}
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墨雨无痕
6楼-- · 2018-12-31 09:19

Or since Objective C is just C with some OO layer on top you can use the posix conterparts:

int execl(const char *path, const char *arg0, ..., const char *argn, (char *)0);
int execle(const char *path, const char *arg0, ..., const char *argn, (char *)0, char *const envp[]);
int execlp(const char *file, const char *arg0, ..., const char *argn, (char *)0);
int execlpe(const char *file, const char *arg0, ..., const char *argn, (char *)0, char *const envp[]);
int execv(const char *path, char *const argv[]);
int execve(const char *path, char *const argv[], char *const envp[]);
int execvp(const char *file, char *const argv[]);
int execvpe(const char *file, char *const argv[], char *const envp[]); 

They are included from unistd.h header file.

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何处买醉
7楼-- · 2018-12-31 09:20

Objective-C (see below for Swift)

Cleaned up the code in the top answer to make it more readable, less redundant, added the benefits of the one-line method and made into an NSString category

@interface NSString (ShellExecution)
- (NSString*)runAsCommand;
@end

Implementation:

@implementation NSString (ShellExecution)

- (NSString*)runAsCommand {
    NSPipe* pipe = [NSPipe pipe];

    NSTask* task = [[NSTask alloc] init];
    [task setLaunchPath: @"/bin/sh"];
    [task setArguments:@[@"-c", [NSString stringWithFormat:@"%@", self]]];
    [task setStandardOutput:pipe];

    NSFileHandle* file = [pipe fileHandleForReading];
    [task launch];

    return [[NSString alloc] initWithData:[file readDataToEndOfFile] encoding:NSUTF8StringEncoding];
}

@end

Usage:

NSString* output = [@"echo hello" runAsCommand];

And if you're having problems with output encoding:

// Had problems with `lsof` output and Japanese-named files, this fixed it
NSString* output = [@"export LANG=en_US.UTF-8;echo hello" runAsCommand];

Hope it's as useful to you as it will be to future me. (Hi, you!)


Swift 4

Here's a Swift example making use of Pipe, Process, and String

extension String {
    func run() -> String? {
        let pipe = Pipe()
        let process = Process()
        process.launchPath = "/bin/sh"
        process.arguments = ["-c", self]
        process.standardOutput = pipe

        let fileHandle = pipe.fileHandleForReading
        process.launch()

        return String(data: fileHandle.readDataToEndOfFile(), encoding: .utf8)
    }
}

Usage:

let output = "echo hello".run()
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