Command Line Arguments

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Command Line Arguments

• Soon Tee Teoh
• CS 49C

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The main( ) function

• So far, we have been defining the main() function
  to receive no arguments.
• Actually, the main( ) function can receive two
  arguments.
• To do that, the main( ) function should be
  defined as below.
• This is how arguments can be passed in at the
  command line.

int main(int argc, char argv )
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Command Line Arguments

• From the command prompt, we can start running a
  program by typing its name and pressing ENTER.
• To pass arguments, we type in the programs name
  followed by some arguments, then press ENTER.
• Below is an example from the Unix command prompt.

myprog
myprog 5 23
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argc and argv

• When the program is called from the command line
  with arguments, argc will contain the number of
  arguments.
• When the user types in arguments, the user
  separates each argument with a space.
• argv is an array of character strings.
• argv1 is the character string containing the
  first argument, argv2 the second, etc.
• Note argv0 contains the character string that
  is the name of the executable.

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Example
int main(int argc, char argv) int
i for (i 1 i lt argc i)
printf("s ", argvi) printf("\n")
return 0
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Using sscanf to get floats and ints

• Suppose you expect an integer and a floating
  point number as command line arguments.
• They will be put in argv1 and argv2
  respectively.
• Use sscanf to get their values.

int main(int argc, char argv) int
n float f sscanf(argv1,
d, n) sscanf(argv2, f, f)