How can I execute a terminal command (like grep) from my Objective-C Cocoa application?
This question is related to
objective-c
cocoa
macos
There is also good old POSIX system("echo -en '\007'");
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.
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");
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.
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 <stdlib.h>
#include <unistd.h>
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(&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.
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.
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,
&authorizationRef);
char *command= "/usr/bin/touch";
char *args[] = {"/System/Library/Caches/com.stackoverflow.test", nil};
err = AuthorizationExecuteWithPrivileges(authorizationRef,
command,
kAuthorizationFlagDefaults,
args,
&pipe);
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!)
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()
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] > 0); // [file availableData] Returns empty data when the pipe was closed
// Task has stopped
[file closeFile];
}
Changes for Swift 3.0:
NSPipehas been renamedPipe
NSTaskhas been renamedProcess
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 {
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 ---"
}
}
}
let input = "echo hello"
let output = input.runAsCommand()
print(output) // prints "hello"
or just:
print("echo hello".runAsCommand()) // prints "hello"
@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.
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");
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] > 0); // [file availableData] Returns empty data when the pipe was closed
// Task has stopped
[file closeFile];
}
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,
&authorizationRef);
char *command= "/usr/bin/touch";
char *args[] = {"/System/Library/Caches/com.stackoverflow.test", nil};
err = AuthorizationExecuteWithPrivileges(authorizationRef,
command,
kAuthorizationFlagDefaults,
args,
&pipe);
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]; });
}
There is also good old POSIX system("echo -en '\007'");
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]; });
}
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
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 <stdlib.h>
#include <unistd.h>
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(&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.
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!)
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()
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.
Changes for Swift 3.0:
NSPipehas been renamedPipe
NSTaskhas been renamedProcess
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 {
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 ---"
}
}
}
let input = "echo hello"
let output = input.runAsCommand()
print(output) // prints "hello"
or just:
print("echo hello".runAsCommand()) // prints "hello"
@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.
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
There is also good old POSIX system("echo -en '\007'");
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 <stdlib.h>
#include <unistd.h>
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(&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.
Source: Stackoverflow.com