Ramblings Of a Madman

Yeah, like i would know a good description…

Posts for Tag: task

"Call piped shell commands from Objective-C"

If you happen to want to know how to run - say - the following command from inside an Objective-C application:

echo "something something" | multimarkdown

So that the fantastic [MultiMarkdown](http://fletcherpenney.net/multimarkdown/) runs its magic and transforms **something something** into **\something something\**, then you need to do as below:

- (NSString*) convertMD:(NSString *)data {

// Task for echo NSTask *echoTask = [[NSTask alloc] init]; [echoTask setLaunchPath: @"/bin/echo"]; // Tell which command we are running [echoTask setArguments: [NSArray arrayWithObjects:data, nil]];

// Task for multimarkdown NSTask *mdTask = [[NSTask alloc] init]; // Make a new task [mdTask setLaunchPath: @"/usr/local/bin/multimarkdown"]; // Tell which command we are running [mdTask setArguments: [NSArray arrayWithObjects:@"--snippet", nil]];

// Pipes for input and output NSPipe *pipeBetween = [NSPipe pipe]; // Handles getting the result of echo and injecting into md NSPipe *outPipe = [NSPipe pipe]; // Handles getting the result of md

// Rig it together [echoTask setStandardOutput:pipeBetween]; [mdTask setStandardInput:pipeBetween]; [mdTask setStandardOutput:outPipe];

// Execute [echoTask launch]; [mdTask launch];

// And get the result data NSData *result = [[outPipe fileHandleForReading] readDataToEndOfFile];

return [[NSString alloc] initWithData:result encoding:NSUTF8StringEncoding]; }

A couple of notes here:

- What this does is pipe the result of the echoTask (which will run **echo "\"**) as input (standard) to the mdTask, which will run **multimarkdown --snippet**; - The outPipe will simply take the output of the mdTask so we can return what multimarkdown created; - The commands need the full path in order for the tasks to run; - In case you are curious, i'm creating a markdown editor for OSX with realtime preview inline; - If you want to test this particular piece of code as-is, make sure you [install multimarkdown for OSX first](http://fletcherpenney.net/multimarkdown/download/).

Peace