Execute a terminal command from a Cocoa app

Question

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

User · Answer

fork  exec  and wait should work  if you re not really looking for a Objective-C specific way  fork creates a copy of the currently running program  exec replaces the currently running program with a new one  and wait waits for the subprocess to exit  For example  without any error checking     include  lt stdlib h gt   include  lt unistd h gt      pid t p   fork    if  p    0           fork returns 0 in the child process         execl   other program to run     other program to run    foo   NULL     else          fork returns the child s PID in the parent         int status      wait  amp status          The child has exited  and status contains the way it exited           The child has run and exited by the time execution gets to here       There s also system  which runs the command as if you typed it from the shell s command line  It s simpler  but you have less control over the situation   I m assuming you re working on a Mac application  so the links are to Apple s documentation for these functions  but they re all POSIX  so you should be to use them on any POSIX-compliant system

User · Answer

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

User · Answer

kent s article gave me a new idea  this runCommand method doesn t need a script file  just runs a command by a line   -  NSString   runCommand  NSString   commandToRun       NSTask  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    NSPipe pipe        task setStandardOutput pipe        NSFileHandle  file    pipe fileHandleForReading         task launch        NSData  data    file readDataToEndOfFile        NSString  output     NSString alloc  initWithData data encoding NSUTF8StringEncoding       return output      You can use this method like this   NSString  output   runCommand   ps -A   grep mysql

User · Answer

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   - gt  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

User · Answer

There is also good old POSIX system  echo -en   007

User · Answer

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 nbsp  nbsp String runAsCommand   nbsp  nbsp -  nbsp  nbsp String  extension String       func runAsCommand   - gt  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     nbsp  nbsp  nbsp  nbsp 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

User · Answer

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  amp  stderr streams for processing data with NSTask   Source code of asynctask m is available at GitHub

User · Answer

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  gt  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

User · Answer

You can use NSTask  Here s an example that would run   usr bin grep foo bar txt      int pid     NSProcessInfo processInfo  processIdentifier   NSPipe  pipe    NSPipe pipe   NSFileHandle  file   pipe fileHandleForReading   NSTask  task     NSTask alloc  init   task launchPath      usr bin grep   task arguments       foo     bar txt    task standardOutput   pipe    task launch    NSData  data    file readDataToEndOfFile    file closeFile    NSString  grepOutput     NSString alloc  initWithData  data encoding  NSUTF8StringEncoding   NSLog    grep returned  n     grepOutput     NSPipe and NSFileHandle are used to redirect the standard output of the task    For more detailed information on interacting with the operating system from within your Objective-C application  you can see this document on Apple s Development Center  Interacting with the Operating System    Edit  Included fix for NSLog problem  If you are using NSTask to run a command-line utility via bash  then you need to include this magic line to keep NSLog working     The magic line that keeps your log where it belongs task standardOutput   pipe    An explanation is here  https   web archive org web 20141121094204 https   cocoadev com HowToPipeCommandsWithNSTask

User · Answer

If the Terminal command requires Administrator Privilege  aka sudo   use AuthorizationExecuteWithPrivileges instead  The following will create a file named  com stackoverflow test  is the root directory   System Library Caches    AuthorizationRef authorizationRef  FILE  pipe   NULL  OSStatus err   AuthorizationCreate nil                                     kAuthorizationEmptyEnvironment                                     kAuthorizationFlagDefaults                                      amp authorizationRef    char  command    usr bin touch   char  args        System Library Caches com stackoverflow test   nil    err   AuthorizationExecuteWithPrivileges authorizationRef                                           command                                           kAuthorizationFlagDefaults                                           args                                            amp pipe

User · Answer

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

User · Answer

There is also good old POSIX system  echo -en   007

User · Answer

There is also good old POSIX system  echo -en   007

User · Answer

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

User · Answer

You can use NSTask  Here s an example that would run   usr bin grep foo bar txt      int pid     NSProcessInfo processInfo  processIdentifier   NSPipe  pipe    NSPipe pipe   NSFileHandle  file   pipe fileHandleForReading   NSTask  task     NSTask alloc  init   task launchPath      usr bin grep   task arguments       foo     bar txt    task standardOutput   pipe    task launch    NSData  data    file readDataToEndOfFile    file closeFile    NSString  grepOutput     NSString alloc  initWithData  data encoding  NSUTF8StringEncoding   NSLog    grep returned  n     grepOutput     NSPipe and NSFileHandle are used to redirect the standard output of the task    For more detailed information on interacting with the operating system from within your Objective-C application  you can see this document on Apple s Development Center  Interacting with the Operating System    Edit  Included fix for NSLog problem  If you are using NSTask to run a command-line utility via bash  then you need to include this magic line to keep NSLog working     The magic line that keeps your log where it belongs task standardOutput   pipe    An explanation is here  https   web archive org web 20141121094204 https   cocoadev com HowToPipeCommandsWithNSTask

User · Answer

fork  exec  and wait should work  if you re not really looking for a Objective-C specific way  fork creates a copy of the currently running program  exec replaces the currently running program with a new one  and wait waits for the subprocess to exit  For example  without any error checking     include  lt stdlib h gt   include  lt unistd h gt      pid t p   fork    if  p    0           fork returns 0 in the child process         execl   other program to run     other program to run    foo   NULL     else          fork returns the child s PID in the parent         int status      wait  amp status          The child has exited  and status contains the way it exited           The child has run and exited by the time execution gets to here       There s also system  which runs the command as if you typed it from the shell s command line  It s simpler  but you have less control over the situation   I m assuming you re working on a Mac application  so the links are to Apple s documentation for these functions  but they re all POSIX  so you should be to use them on any POSIX-compliant system

User · Answer

fork  exec  and wait should work  if you re not really looking for a Objective-C specific way  fork creates a copy of the currently running program  exec replaces the currently running program with a new one  and wait waits for the subprocess to exit  For example  without any error checking     include  lt stdlib h gt   include  lt unistd h gt      pid t p   fork    if  p    0           fork returns 0 in the child process         execl   other program to run     other program to run    foo   NULL     else          fork returns the child s PID in the parent         int status      wait  amp status          The child has exited  and status contains the way it exited           The child has run and exited by the time execution gets to here       There s also system  which runs the command as if you typed it from the shell s command line  It s simpler  but you have less control over the situation   I m assuming you re working on a Mac application  so the links are to Apple s documentation for these functions  but they re all POSIX  so you should be to use them on any POSIX-compliant system

User · Answer

In addition to the several excellent answers above  I use the following code to process the output of the command in the background and avoid the blocking mechanism of  file readDataToEndOfFile    -  void runCommand  NSString   commandToRun       NSTask  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    NSPipe pipe        task setStandardOutput pipe        NSFileHandle  file    pipe fileHandleForReading         task launch         self performSelectorInBackground  selector collectTaskOutput   withObject file      -  void collectTaskOutput  NSFileHandle   file       NSData       data      do               data    file availableData           NSLog          NSString alloc  initWithData data encoding NSUTF8StringEncoding            while   data length   gt  0       file availableData  Returns empty data when the pipe was closed         Task has stopped      file closeFile

User · Answer

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  gt  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

User · Answer

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

User · Answer

fork  exec  and wait should work  if you re not really looking for a Objective-C specific way  fork creates a copy of the currently running program  exec replaces the currently running program with a new one  and wait waits for the subprocess to exit  For example  without any error checking     include  lt stdlib h gt   include  lt unistd h gt      pid t p   fork    if  p    0           fork returns 0 in the child process         execl   other program to run     other program to run    foo   NULL     else          fork returns the child s PID in the parent         int status      wait  amp status          The child has exited  and status contains the way it exited           The child has run and exited by the time execution gets to here       There s also system  which runs the command as if you typed it from the shell s command line  It s simpler  but you have less control over the situation   I m assuming you re working on a Mac application  so the links are to Apple s documentation for these functions  but they re all POSIX  so you should be to use them on any POSIX-compliant system

User · Answer

in the spirit of sharing    this is a method I use frequently to run shell scripts  you can add a script to your product bundle  in the copy phase of the build  and then have the script be read and run at runtime   note  this code looks for the script in the privateFrameworks sub-path  warning  this could be a security risk for deployed products  but for our in-house development it is an easy way to customize simple things  like which host to rsync to     without re-compiling the application  but just editing the shell script in the bundle     ------------------------------------------------------ - void  runScript  NSString  scriptName       NSTask  task      task     NSTask alloc  init        task setLaunchPath     bin sh         NSArray  arguments      NSString  newpath    NSString stringWithFormat            NSBundle mainBundle  privateFrameworksPath   scriptName       NSLog   shell script path      newpath       arguments    NSArray arrayWithObjects newpath  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    script returned  n     string           ------------------------------------------------------   Edit  Included fix for NSLog problem  If you are using NSTask to run a command-line utility via bash  then you need to include this magic line to keep NSLog working     The magic line that keeps your log where it belongs  task setStandardInput  NSPipe pipe      In context   NSPipe  pipe  pipe    NSPipe pipe    task setStandardOutput  pipe     The magic line that keeps your log where it belongs  task setStandardInput  NSPipe pipe      An explanation is here  http   www cocoadev com index pl NSTask

User · Answer

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   - gt  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

User · Answer

You can use NSTask  Here s an example that would run   usr bin grep foo bar txt      int pid     NSProcessInfo processInfo  processIdentifier   NSPipe  pipe    NSPipe pipe   NSFileHandle  file   pipe fileHandleForReading   NSTask  task     NSTask alloc  init   task launchPath      usr bin grep   task arguments       foo     bar txt    task standardOutput   pipe    task launch    NSData  data    file readDataToEndOfFile    file closeFile    NSString  grepOutput     NSString alloc  initWithData  data encoding  NSUTF8StringEncoding   NSLog    grep returned  n     grepOutput     NSPipe and NSFileHandle are used to redirect the standard output of the task    For more detailed information on interacting with the operating system from within your Objective-C application  you can see this document on Apple s Development Center  Interacting with the Operating System    Edit  Included fix for NSLog problem  If you are using NSTask to run a command-line utility via bash  then you need to include this magic line to keep NSLog working     The magic line that keeps your log where it belongs task standardOutput   pipe    An explanation is here  https   web archive org web 20141121094204 https   cocoadev com HowToPipeCommandsWithNSTask

User · Answer

in the spirit of sharing    this is a method I use frequently to run shell scripts  you can add a script to your product bundle  in the copy phase of the build  and then have the script be read and run at runtime   note  this code looks for the script in the privateFrameworks sub-path  warning  this could be a security risk for deployed products  but for our in-house development it is an easy way to customize simple things  like which host to rsync to     without re-compiling the application  but just editing the shell script in the bundle     ------------------------------------------------------ - void  runScript  NSString  scriptName       NSTask  task      task     NSTask alloc  init        task setLaunchPath     bin sh         NSArray  arguments      NSString  newpath    NSString stringWithFormat            NSBundle mainBundle  privateFrameworksPath   scriptName       NSLog   shell script path      newpath       arguments    NSArray arrayWithObjects newpath  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    script returned  n     string           ------------------------------------------------------   Edit  Included fix for NSLog problem  If you are using NSTask to run a command-line utility via bash  then you need to include this magic line to keep NSLog working     The magic line that keeps your log where it belongs  task setStandardInput  NSPipe pipe      In context   NSPipe  pipe  pipe    NSPipe pipe    task setStandardOutput  pipe     The magic line that keeps your log where it belongs  task setStandardInput  NSPipe pipe      An explanation is here  http   www cocoadev com index pl NSTask

User · Answer

If the Terminal command requires Administrator Privilege  aka sudo   use AuthorizationExecuteWithPrivileges instead  The following will create a file named  com stackoverflow test  is the root directory   System Library Caches    AuthorizationRef authorizationRef  FILE  pipe   NULL  OSStatus err   AuthorizationCreate nil                                     kAuthorizationEmptyEnvironment                                     kAuthorizationFlagDefaults                                      amp authorizationRef    char  command    usr bin touch   char  args        System Library Caches com stackoverflow test   nil    err   AuthorizationExecuteWithPrivileges authorizationRef                                           command                                           kAuthorizationFlagDefaults                                           args                                            amp pipe

User · Answer

You can use NSTask  Here s an example that would run   usr bin grep foo bar txt      int pid     NSProcessInfo processInfo  processIdentifier   NSPipe  pipe    NSPipe pipe   NSFileHandle  file   pipe fileHandleForReading   NSTask  task     NSTask alloc  init   task launchPath      usr bin grep   task arguments       foo     bar txt    task standardOutput   pipe    task launch    NSData  data    file readDataToEndOfFile    file closeFile    NSString  grepOutput     NSString alloc  initWithData  data encoding  NSUTF8StringEncoding   NSLog    grep returned  n     grepOutput     NSPipe and NSFileHandle are used to redirect the standard output of the task    For more detailed information on interacting with the operating system from within your Objective-C application  you can see this document on Apple s Development Center  Interacting with the Operating System    Edit  Included fix for NSLog problem  If you are using NSTask to run a command-line utility via bash  then you need to include this magic line to keep NSLog working     The magic line that keeps your log where it belongs task standardOutput   pipe    An explanation is here  https   web archive org web 20141121094204 https   cocoadev com HowToPipeCommandsWithNSTask

User · Answer

In addition to the several excellent answers above  I use the following code to process the output of the command in the background and avoid the blocking mechanism of  file readDataToEndOfFile    -  void runCommand  NSString   commandToRun       NSTask  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    NSPipe pipe        task setStandardOutput pipe        NSFileHandle  file    pipe fileHandleForReading         task launch         self performSelectorInBackground  selector collectTaskOutput   withObject file      -  void collectTaskOutput  NSFileHandle   file       NSData       data      do               data    file availableData           NSLog          NSString alloc  initWithData data encoding NSUTF8StringEncoding            while   data length   gt  0       file availableData  Returns empty data when the pipe was closed         Task has stopped      file closeFile

User · Answer

kent s article gave me a new idea  this runCommand method doesn t need a script file  just runs a command by a line   -  NSString   runCommand  NSString   commandToRun       NSTask  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    NSPipe pipe        task setStandardOutput pipe        NSFileHandle  file    pipe fileHandleForReading         task launch        NSData  data    file readDataToEndOfFile        NSString  output     NSString alloc  initWithData data encoding NSUTF8StringEncoding       return output      You can use this method like this   NSString  output   runCommand   ps -A   grep mysql

User · Answer

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  amp  stderr streams for processing data with NSTask   Source code of asynctask m is available at GitHub

User · Answer

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 nbsp  nbsp String runAsCommand   nbsp  nbsp -  nbsp  nbsp String  extension String       func runAsCommand   - gt  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     nbsp  nbsp  nbsp  nbsp 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

User · Answer

There is also good old POSIX system  echo -en   007

[objective-c] Execute a terminal command from a Cocoa app

Examples related to objective-c

Examples related to cocoa

Examples related to macos