Argument processing
- C course
- Intermediate
- Lesson 89/116
- 5 min
Learn to process arguments by looping over argv.
Loop over arguments
To process arguments you set up a for loop from argv[1] to argv[argc-1]. At each step argv[i] gives the corresponding string.
Example: for (int i = 1; i < argc; i++) printf("%s\n", argv[i]);. The loop starts at i = 1 because argv[0] is the program name and is usually skipped. The %s conversion prints a string. This pattern underlies tools that take multiple inputs such as file lists or search terms.
Simulated arguments
To try the argument-processing pattern without run-time input, declare a local array resembling argv. This keeps the output always the same.
Example: char *args[] = {"prog", "apple", "pear"}; int n = 3;. Then for (int i = 1; i < n; i++) printf("%s\n", args[i]);. This technique helps when testing command-line tools: put a fixed array in place of real argv and verify the expected output. The same loop pattern works for both simulation and real arguments.
Practice Print simulated arguments
Declare char *args[] = {"prog", "elma", "armut", "portakal"}; and int n = 4;. Loop with for (int i = 1; i < n; i++) and print each argument with printf("%s\n", args[i]);.
Starter code
#include <stdio.h>
// Define the args array and the count n
// Loop over each argument and print it
int main(void) {
return 0;
}Sample solution
#include <stdio.h>
int main(void) {
char *args[] = {"prog", "elma", "armut", "portakal"};
int n = 4;
for (int i = 1; i < n; i++) {
printf("%s\n", args[i]);
}
return 0;
}Expected output
elma armut portakal
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 Match the loop parts
| Term | Meaning |
|---|---|
i = 1 |
Start value |
i < argc |
Continuation test |
i++ |
Step increment |
argv[i] |
Current string |
2 Why does the loop start at i = 1?
- Because loops must start at 1
- Because argc cannot be at least 1
- Because argv[0] is always NULL
- Because argv[0] is the program name Correct answer
Explanation: argv[0] holds the program name; real user arguments start at argv[1].
3 Complete the loop condition
for (int i = 1; i < ____; i++)for (int i = 1; i < argc; i++)Explanation: The test i < argc runs the loop up to the last argument.