1 files changed, 51 insertions, 0 deletions
diff --git a/src/factor.c b/src/factor.c
new file mode 100644
index 0000000..9443fd8
--- /dev/null
+++ b/src/factor.c
@@ -0,0 +1,51 @@
+#define _POSIX_C_SOURCE 200809L
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <ctype.h>
+#include <errno.h>
+
+int g_status_code = 0;
+
+void print_factors(const char *s)
+{
+	char *endptr;
+	errno = 0;
+	unsigned long n = strtoul(s, &endptr, 10);
+	if (errno != 0 || !isdigit(*s) || *endptr != '\0')
+	{
+		fprintf(stderr, "factor: '%s': is not a valid positive integer\n", s);
+		g_status_code = 1;
+		return;
+	}
+	printf("%lu:", n);
+	while (n > 1)
+	{
+		for (unsigned long d = 2; true; d++)
+		{
+			if (n % d == 0)
+			{
+				printf(" %lu", d);
+				n /= d;
+				break;
+			}
+		}
+	}
+	fputc('\n', stdout);
+}
+
+int main(int argc, char **argv)
+{
+	if (argc == 1)
+	{
+		char *line = NULL;
+		size_t n = 0;
+		while (getline(&line, &n, stdin) != -1)
+			print_factors(line);
+		free(line);
+		return g_status_code;
+	}
+	for (int i = 1; i < argc; i++)
+		print_factors(argv[i]);
+	return g_status_code;
+}