Handling command-line arguments is a very common task. Here are snippets of code I use to handle command line arguments in Python, Java and C.
Command-line arguments in Python
import sys
# sys.argv is a list of strings.
# argv[0] is the script name
for arg in sys.argv:
# do something with the argument
print arg
$ python cmd_line_args.py Position1 Position2 Position3
cmd_line_args.py
Position1
Position2
Position3
$ python cmd_line_args.py "Position1 Position2 Position3"
cmd_line_args.py
Position1 Position2 Position3
import sys
# sys.argv is a list of strings.
# argv[0] is the script name
for arg in sys.argv[1:]:
# if you are sure that the arguments are integers
arg_int = int(arg)
# do something with the argument
print arg_int
$ python cmd_line_args.py 2013 6 30
2013
6
30
$ python cmd_line_args.py Position1 Position2 Position3
Traceback (most recent call last):
File "cmd_line_args.py", line 6, in <module>
arg_int = int(arg)
ValueError: invalid literal for int() with base 10: 'Position1'
Reference: Python Tutorial.
For more advanced needs, you can try the argparse module.
Command-line arguments in Java
public class CommandLineArguments {
public static void main(String[] args) {
// args is an array of Strings
// You can access various positional arguments using
// args[0], args[1], etc. Or you can iterate over them.
for (String argument : args) {
// do something with the argument
System.out.println(argument);
}
}
}
$ javac CommandLineArguments.java
$ java CommandLineArguments Position1 Position2 Position3
Position1
Position2
Position3
$ java CommandLineArguments "Position1 Position2 Position3"
Position1 Position2 Position3
public class CommandLineArgumentsInt {
public static void main(String[] args) {
// args is an array of Strings
// You can access various positional arguments using
// args[0], args[1], etc. Or you can iterate over them.
for (String argument : args) {
// If you are sure that the arguments are integers
int arg = Integer.parseInt(argument);
// do something with the argument
System.out.println(arg);
}
}
}
$ javac CommandLineArgumentsInt.java
$ java CommandLineArgumentsInt 2013 6 30
2013
6
30
$ java CommandLineArgumentsInt Position1 Position2 Position3
Exception in thread "main" java.lang.NumberFormatException: For input string: "Position1"
at java.lang.NumberFormatException.forInputString(NumberFormatException.java:48)
at java.lang.Integer.parseInt(Integer.java:449)
at java.lang.Integer.parseInt(Integer.java:499)
at CommandLineArgumentsInt.main(CommandLineArgumentsInt.java:8)
Reference: The Java Tutorial.
For more advanced needs, see this Stack Overflow question.
Command-line arguments in C
#include <stdio.h>
int main(int argc, char* argv[]) {
// argc refers to the number of arguments passed.
// argv is an array of char pointers which contain the passed arguments.
// argv[0] is the path and name of the program itself
for (int i = 0; i < argc; i++) {
// do something whith the argument
printf("%s\n", argv[i]);
}
}
$ cc cmd_line_args.c
$ ./a.out Position1 Position2 Position3
./a.out
Position1
Position2
Position3
$ ./a.out "Position1 Position2 Position3"
./a.out
Position1 Position2 Position3
#include <stdio.h>
#include <stdlib.h>
int main(int argc, char* argv[]) {
// argc refers to the number of arguments passed.
// argv is an array of char pointers which contain the passed arguments.
// argv[0] is the path and name of the program itself
for (int i = 1; i < argc; i++) {
// If you are sure that the arguments are integers
int argument = atoi(argv[i]);
// do something whith the argument
printf("%d\n", argument);
}
}
$ cc cmd_line_args.c
$ ./a.out 2013 6 30
2013
6
30
$ ./a.out Position1 Position2 Position3
0
0
0
For more advanced needs, use getopt.
