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C Command-Line Args

This lesson is part of C · All levels

Summary

The play function can receive arguments from the command row through int main(int argc, char *argv[]), where argc is the number of arguments and argv is the array string of arguments. argv[0] usually contains the name of the program so the user argument starts with argv[1]. Since all arguments are string-shaped, convert to a number with strtol, atoi, or sscanf before using the count.

Key points

Argc is always a minimum of 1, and argv[argc] is guaranteed to be worth NULL as the end marker of the list.
Argv[0] contains the name or path of the program, while the user argument begins with argv[1].
Parsing numbers should be using a strtol that can detect errors, not a failure-witness tool.
The general format of an argument-based program is the option to pass data, e.g. the program -v file.txt.
Check the options using strcmp, for example strcmp(argv[1], "-h") == 0.

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