Command-line arguments in the C language
R.C. Maher EE475 Fall 2004
The C language provides a method to pass parameters to the main() function. This is
typically accomplished by specifying arguments on the operating system command line
(console).
The prototype for main() looks like:
int main(int argc, char *argv[])
{
…
}
There are two parameters passed to main(). The first parameter is the number of items
on the command line (int argc). Each argument on the command line is separated by
one or more spaces, and the operating system places each argument directly into its own
null-terminated string. The second parameter passed to main() is an array of pointers
to the character strings containing each argument (char *argv[]).
For example, at the command prompt:
test_prog 1 apple orange 4096.0
There are 5 items on the command line, so the operating system will set argc=5 . The
parameter argv is a pointer to an array of pointers to strings of characters, such that:
argv[0] is a pointer to the string “test_prog”
argv[1] is a pointer to the string “1”
argv[2] is a pointer to the string “apple”
argv[3] is a pointer to the string “orange”
and
argv[4] is a pointer to the string “4096.0”
Notes
• The main() routine can check argc to see how many arguments the user
specified.
• The minimum count for argc is 1: the command line just contained the name of
the invoked program with no arguments.
• The program can find out its own name as it was invoked: it is stored in the
argv[0] string! Some operating systems don't provide this feature, however.
• The arguments from the command line are not automatically converted: the
characters are just copied into the argv strings.
1
