Objective C Command Line Arguments - Objective C

What are Objective C Command-Line Arguments?

Some values passed to the command line programs when they are executed are called command line arguments.
These are important in a program especially when you want to control the program form outside of hard coding those inside the code.
The command line arguments are handled using main() function arguments where

• argc refers to the number of arguments passed
• argv[] is a pointer array, which points to each argument passed to the program.

A simple example is illustrated to check if there is any argument supplied from the command line and take action accordingly:

#import <Foundation/Foundation.h> int main( int argc, char *argv[] ) { if( argc == 2 ) { NSLog(@"The argument supplied is %s\n", argv[1]); } else if( argc > 2 ) { NSLog(@"Too many arguments supplied.\n"); } else { NSLog(@"One argument expected.\n"); } }

The above code is compiled and executed with a single argument, say "testing", the following result is produced.

2013-09-13 03:01:17.333 demo[7640] The argument supplied is testing

The above code is compiled and executed with two arguments, say testing1 and testing2, it produces the following result.

2013-09-13 03:01:18.333 demo[7640] Too many arguments supplied.

When the above code is compiled and executed without passing any argument, it produces the following result.

2013-09-13 03:01:18.333 demo[7640] One argument expected

It should be noted that

• argv[0] holds the name of the program itself
• argv[1] is a pointer to the first command-line argument supplied *argv[n] is the last argument.
• If no arguments are supplied, argc will be one, otherwise if you pass one argument, then argc is set at 2.

All the command line arguments are separated by a space, but if argument itself has a space, then you can pass such arguments by putting them inside double quotes "" or single quotes ''.

The above example is rewritten where, we will print program name and pass a command-line argument by putting inside double quotes:

#import <Foundation/Foundation.h> int main( int argc, char *argv[] ) { NSLog(@"Program name %s\n", argv[0]); if( argc == 2 ) { NSLog(@"The argument supplied is %s\n", argv[1]); } else if( argc > 2 ) { NSLog(@"Too many arguments supplied.\n"); } else { NSLog(@"One argument expected.\n"); } return 0; }

The above code is compiled and executed with a single argument separated by space but inside double quotes say "Testing1 Testing2", it produces the following result.

2013-09-14 04:07:57.305 demo[8534] Program name demo 2013-09-14 04:07:57.305 demo[8534] The argument supplied is Testing1 Testing 2