1 files changed, 53 insertions, 0 deletions
diff --git a/trigraph.c b/trigraph.c
new file mode 100644
index 0000000..b80b198
--- /dev/null
+++ b/trigraph.c
@@ -0,0 +1,53 @@
+#include <stdio.h>
+
+int main(int argc, char *argv[])
+{
+	FILE *in = stdin;
+
+	if (argc > 2) {
+		printf("usage: %s [file]\n", argv[0]);
+		return 1;
+	}
+
+	if (argc == 2) {
+		in = fopen(argv[1], "r");
+		if (in == NULL) {
+			perror(argv[1]);
+			return 1;
+		}
+	}
+
+	int c;
+	int q = 0;
+	while ((c = fgetc(in)) != EOF) {
+		if (q == 2) {
+			switch (c) {
+			case '=':	putchar('#');	break;
+			case '/':	putchar('\\');	break;
+			case '\'':	putchar('^');	break;
+			case '(':	putchar('[');	break;
+			case ')':	putchar(']');	break;
+			case '!':	putchar('|');	break;
+			case '<':	putchar('{');	break;
+			case '>':	putchar('}');	break;
+			case '-':	putchar('~');	break;
+			case '?':	putchar('?');	break;
+
+			default:
+				printf("??%c", c);
+				break;
+			}
+
+			if (c != '?') {
+				q = 0;
+			}
+		} else if (c == '?') {
+			q++;
+		} else {
+			putchar(c);
+			q = 0;
+		}
+	}
+
+	return 0;
+}