I'm trying to execute this comamnd ps -ef | grep test using NSTask but I can't get the | grep test to be included in the NSTask:
This is what I'm using currently to get the output of ps -ef into a string then I need to somehow get the pid of the process test
NSTask *task;
task = [[NSTask alloc] init];
[task setLaunchPath: #"/bin/ps"];
NSArray *arguments;
arguments = [NSArray arrayWithObjects: #"-ef", nil];
[task setArguments: arguments];
NSPipe *pipe;
pipe = [NSPipe pipe];
[task setStandardOutput: pipe];
NSFileHandle *file;
file = [pipe fileHandleForReading];
[task launch];
NSData *data;
data = [file readDataToEndOfFile];
NSString *string;
string = [[NSString alloc] initWithData: data
encoding: NSUTF8StringEncoding];
NSLog (#"got\n%#", string);
Piping is a feature provided by shells, such as /bin/sh. You may try launching your command via such a shell:
/* ... */
[task setLaunchPath: #"/bin/sh"];
/* ... */
arguments = [NSArray arrayWithObjects: #"-c", #"ps -ef | grep test", nil];
However, if you let the user supply a value (instead of hard-coding e.g. test), you are making the program susceptible to shell injection attacks, which are kind of like SQL injection. An alternative, which doesn't suffer from this problem, is to use a pipe object to connect the standard output of ps with the standard input of grep:
NSTask *psTask = [[NSTask alloc] init];
NSTask *grepTask = [[NSTask alloc] init];
[psTask setLaunchPath: #"/bin/ps"];
[grepTask setLaunchPath: #"/bin/grep"];
[psTask setArguments: [NSArray arrayWithObjects: #"-ef", nil]];
[grepTask setArguments: [NSArray arrayWithObjects: #"test", nil]];
/* ps ==> grep */
NSPipe *pipeBetween = [NSPipe pipe];
[psTask setStandardOutput: pipeBetween];
[grepTask setStandardInput: pipeBetween];
/* grep ==> me */
NSPipe *pipeToMe = [NSPipe pipe];
[grepTask setStandardOutput: pipeToMe];
NSFileHandle *grepOutput = [pipeToMe fileHandleForReading];
[psTask launch];
[grepTask launch];
NSData *data = [grepOutput readDataToEndOfFile];
/* etc. */
This uses built-in Foundation functionality to perform the same steps as the shell does when it encounters the | character.
Finally as others have pointed out, the usage of grep is overkill. Just add this to your code:
NSArray *lines = [string componentsSeparatedByString:#"\n"];
NSArray *filteredLines = [lines filteredArrayUsingPredicate: [NSPredicate predicateWithFormat: #"SELF contains[c] 'test'"]];
You may need to call [task waitUntilExit] before you launch the task, so that the process can finish running before you read the output.
Related
I am trying to retrieve CPU usage of system using
top -F -R -o cpu
The command is running fine in terminal however I am not able to get the output in Objective c using the code given below:
-(NSString*)runCommand:(NSString*)commandToRun;
{
NSTask *task;
task = [[NSTask alloc] init];
[task setLaunchPath: #"/bin/sh"];
NSArray *arguments = [NSArray arrayWithObjects:
#"-c" ,
[NSString stringWithFormat:#"%#", commandToRun],
nil];
NSLog(#"run command: %#",commandToRun);
[task setArguments: arguments];
NSPipe *pipe;
pipe = [NSPipe pipe];
[task setStandardOutput: pipe];
NSFileHandle *file;
file = [pipe fileHandleForReading];
[task launch];
NSData *data;
data = [file readDataToEndOfFile];
NSString *output;
output = [[NSString alloc] initWithData: data encoding: NSUTF8StringEncoding];
return output;
}
I am getting the empty string as a result.
Please suggest what should I do. Many thanks.
I haven't tried using top before in this way, I suspect the issue is related to top updating the output every second. In that case you could try a different top command:
top -F -R -o cpu -l 1
or use a different tool to get the data you want, like ps:
ps -vaA
I am trying to run sudo command programmatically in my OS X app,
but i got these message
sudo: no tty present and no askpass program specified
Here is my code:
NSString *runCommand(NSString *commandToRun)
{
NSTask *task;
task = [[NSTask alloc] init];
[task setLaunchPath: #"/bin/sh"];
NSArray *arguments = [NSArray arrayWithObjects:#"-c" ,[NSString stringWithFormat:#"%#", commandToRun], nil];
NSLog(#"run command: %#",commandToRun);
[task setArguments: arguments];
NSPipe *pipe;
pipe = [NSPipe pipe];
[task setStandardOutput: pipe];
NSFileHandle *file;
file = [pipe fileHandleForReading];
[task launch];
NSData *data;
data = [file readDataToEndOfFile];
NSString *output;
output = [[NSString alloc] initWithData: data encoding: NSUTF8StringEncoding];
return output;
}
And i call this method like this :
runCommand(#"sudo purge");
Thanks for any help or sugession.
I want to execute a command from objective C (Cocoa framework). The command I am trying is as below. I tried with NSTask but it says "launch path not accessible" when I execute it.
sudo ifconfig en0 down
My code is:
- (void)testme {
NSTask *task;
task = [[NSTask alloc] init];
[task setLaunchPath: #"sudo ifconfig en0 down"];
NSArray *arguments;
arguments = [NSArray arrayWithObjects: #"foo", #"bar.txt", nil];
[task setArguments: arguments];
NSPipe *pipe;
pipe = [NSPipe pipe];
[task setStandardOutput: pipe];
NSFileHandle *file;
file = [pipe fileHandleForReading];
[task launch];
NSData *data;
data = [file readDataToEndOfFile];
NSString *string;
string = [[NSString alloc] initWithData: data encoding: NSUTF8StringEncoding];
NSLog (#"command returned:\n%#", string);
[string release];
[task release];
}
sudo ifconfig en0 down is not a sensible launch path. The correct launch path for this command would be /usr/sbin/sudo.
Once that is done, you still need to pass the correct arguments to setArguments:. foo and bar.txt look like example code that you copied without reading.
MORE IMPORTANTLY, THOUGH, running sudo from NSTask will not work. You will need to use Authorization Services to launch a privileged command.
You need to specify the full executable path and you should specify the arguments as the arguments, not along with the launch path. NSTask ain't a shell, it internally uses syscalls (execv(), I guess) to invoke the command.
NSTask *task = [[NSTask alloc] init];
[task setLaunchPath:#"/usr/bin/sudo"];
NSArray *arguments = #[#"ifconfig", #"en0", #"down"];
[task setArguments:arguments];
I'm trying to call ffmpeg from NSTask in objective-c. I execute the ffmpeg command in terminal and it works flawlessly every time. I make the same command using NSTask, and it never gives me the whole output. It cuts it off half way through the output, at a seemingly random spot every time. Here is my code.
- (void)applicationDidFinishLaunching:(NSNotification *)aNotification
{
NSString* ffmpegPath = [[NSBundle mainBundle] pathForResource:#"ffmpeg" ofType:#""];
NSString* path = #"test.mov";
NSTask *task = [[NSTask alloc] init];
NSArray *arguments = [NSArray arrayWithObjects: #"-i", path, nil];
NSPipe *pipe = [NSPipe pipe];
NSFileHandle * read = [pipe fileHandleForReading];
[task setLaunchPath: ffmpegPath];
[task setArguments: arguments];
[task setStandardOutput: pipe];
[task launch];
[task waitUntilExit];
NSData* data = [read readDataToEndOfFile];
NSString* stringOutput = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
NSLog(#"%#", stringOutput);
NSLog(#"%i", [task terminationStatus]);
NSLog(#"DONE");
}
And just like that I figured it out. Apparently the output had non UTF8Characters in it. Switched it over to NSASCIIStringEncoding and voila. Magic.
Can someone help me convert the following code into code that instead has two NSTasks for "cat" and "grep", showing how the two can be connected together with pipes? I suppose I would prefer the latter approach, since then I no longer have to worry about quoting and stuff.
NSTask *task;
task = [[NSTask alloc] init];
[task setLaunchPath: #"/bin/sh"];
NSArray *arguments;
arguments = [NSArray arrayWithObjects: #"-c",
#"cat /usr/share/dict/words | grep -i ham", nil];
[task setArguments: arguments];
[task launch];
Update: Note that cat and grep are here just meant as (lousy) example. I still want to do this for commands that make more sense.
Use a instance of NSTask for each program and connect their standard inputs/outputs with NSPipe:
NSPipe *pipe = [[NSPipe alloc] init];
NSPipe *resultPipe = [[NSPipe alloc] init];
NSTask *task1 = [[NSTask alloc] init];
[task1 setLaunchPath: #"/bin/cat"];
[task1 setStandardOutput: pipe];
[task1 launch];
NSTask *task2 = [[NSTask alloc] init];
[task2 setLaunchPath: #"/bin/grep"];
[task2 setStandardInput: pipe];
[task2 setStandardOutput: resultPipe];
[task2 launch];
NSData *result = [[resultPipe fileHandleForReading] readDataToEndOfFile];