ShellTask.m

//
//  ShellTask.m
//  
//
//  Created by Vincent Gable on 6/1/07.
//  Copyright 2007 Vincent Gable, you're free to use this code in *any* way you like, but I'd really appreciate it if you told me what you used it for.  It could make my day.
//

#import "ShellTask.h"

@implementation ShellTask


//Returns an NSTask that is equvalent to 
// sh -c <command>
//where <command> is passed directly to sh via argv, and is NOT quoted (so ~ expansion still works).
//stdin for the task is set to /dev/null .
//Note that the PWD for the task is whatever the current PWD for the executable sending the taskForCommand: message.
//Sending the task a - launch message will tell sh to run it.
+ (NSTask*) taskForShellCommand:(NSString*)command
{
	NSTask *task = [[[NSTask alloc] init] autorelease]; 
	
	// @"/bin/sh" -> @"/bin/bash"
    [task setLaunchPath: @"/bin/bash"]; //we are launching sh, it is wha will process command for us
	[task setStandardInput:[NSFileHandle fileHandleWithNullDevice]]; //stdin is directed to /dev/null
	
	
	NSArray	*args = [NSArray arrayWithObjects:	@"-c", //-c tells sh to execute commands from the next argument
												command, //sh will read and execute the commands in this string.
												nil];
    [task setArguments: args];

    return task;
}


//Executes the shell command, command, waits for it to finish
//returning it's output to std in and stderr.
//
//NOTE: may deadlock under some circumstances if the output gets so big it fills the pipe.
//See http://dev.notoptimal.net/search/label/NSTask for an overview of the problem, and a solution.
//I have not experienced the problem myself, so I can't comment.
+ (NSString*) executeShellCommandSynchronously:(NSString*)command
{
	NSTask *task = [self taskForShellCommand:command];
	
	//we pipe stdout and stderr into a file handle that we read to 
    NSPipe *outputPipe = [NSPipe pipe];
    [task setStandardOutput: outputPipe];
	[task setStandardError: outputPipe];
    NSFileHandle *outputFileHandle = [outputPipe fileHandleForReading];
	
    [task launch];

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

+ (oneway void) executeShellCommandAsynchronously:(NSString*)command
{
	[[self taskForShellCommand:command] launch];
	
	return;
}

@end