Rename mc(1) to cols(1)

There is an obvious name collision with the popular file manager
midnight commander.

cols.c

@@ -0,0 +1,96 @@
+/* See LICENSE file for copyright and license details. */
+#include <assert.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/ioctl.h>
+#include "text.h"
+#include "util.h"
+
+static long chars = 65;
+static int cflag;
+static struct linebuf b = EMPTY_LINEBUF;
+
+static long n_columns;
+static long n_rows;
+
+static void
+usage(void)
+{
+	eprintf("usage: %s [-c chars] [FILE...]\n", argv0);
+}
+
+int
+main(int argc, char *argv[])
+{
+	long i, l, col;
+	size_t maxlen = 0;
+	char *space;
+	struct winsize w;
+	FILE *fp;
+
+	ARGBEGIN {
+	case 'c':
+		cflag = 1;
+		chars = estrtol(EARGF(usage()), 0);
+		if(chars < 3)
+			eprintf("%d: too few character columns");
+		break;
+	default:
+		usage();
+	} ARGEND;
+
+	if (cflag == 0) {
+		ioctl(STDOUT_FILENO, TIOCGWINSZ, &w);
+		if (w.ws_col != 0)
+			chars = w.ws_col;
+	}
+
+	/* XXX librarify this chunk, too?  only useful in sponges though */
+	if(argc == 0) {
+		getlines(stdin, &b);
+	} else for(; argc > 0; argc--, argv++) {
+		if(!(fp = fopen(argv[0], "r")))
+			eprintf("fopen %s:", argv[0]);
+		getlines(fp, &b);
+		fclose(fp);
+	}
+
+	for(l = 0; l < b.nlines; ++l) {
+		size_t len = strlen(b.lines[l]);
+		if(len > 0 && b.lines[l][len-1] == '\n')
+			b.lines[l][--len] = '\0';
+		if(len > maxlen)
+			maxlen = len;
+		if(maxlen > (chars - 1) / 2)
+			break;
+	}
+
+	n_columns = (chars + 1) / (maxlen + 1);
+	if(n_columns <= 1) {
+		for(l = 0; l < b.nlines; ++l) {
+			fputs(b.lines[l], stdout);
+		}
+		return EXIT_SUCCESS;
+	}
+
+	if(!(space = malloc(maxlen + 2)))
+		eprintf("malloc:");
+	memset(space, ' ', maxlen + 1);
+	space[maxlen + 1] = '\0';
+
+	n_rows = (b.nlines + (n_columns - 1)) / n_columns;
+	for(i = 0; i < n_rows; ++i) {
+		for(l = i, col = 1; l < b.nlines; l += n_rows, ++col) {
+			fputs(b.lines[l], stdout);
+			if(col < n_columns)
+				fputs(space + strlen(b.lines[l]), stdout);
+		}
+		fputs("\n", stdout);
+	}
+	free(space);
+
+	return EXIT_SUCCESS;
+}