Add rev(1)

Signed-off-by: Mattias Andrée <maandree@kth.se>

Makefile

@@ -137,6 +137,7 @@ BIN =\
 	pwd\
 	readlink\
 	renice\
+	rev\
 	rm\
 	rmdir\
 	sed\

README

@@ -66,6 +66,7 @@ The following tools are implemented:
 0=*|o pwd             .
 0=*|x readlink        .
 0=*|o renice          .
+0#* x rev             .
 0=*|o rm              (-i)
 0=*|o rmdir           .
  #    sed             .

rev.1

@@ -0,0 +1,22 @@
+.Dd 2016-03-26
+.Dt REV 1
+.Os sbase
+.Sh NAME
+.Nm rev
+.Nd reverse each line
+.Sh SYNOPSIS
+.Nm
+.Op Ar file ...
+.Sh DESCRIPTION
+.Nm
+reads each
+.Ar file
+in sequence and writes it to stdout, but
+with all characters in each line in reverse
+order. If no
+.Ar file
+is given
+.Nm
+reads from stdin.
+.Sh SEE ALSO
+.Xr tac 1

rev.c

@@ -0,0 +1,74 @@
+/* See LICENSE file for copyright and license details. */
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "text.h"
+#include "util.h"
+
+static void
+usage(void)
+{
+	eprintf("usage: %s [file ...]\n", argv0);
+}
+
+static void
+rev(FILE *fp)
+{
+	static char *line = NULL;
+	static size_t size = 0;
+	size_t i;
+	ssize_t n;
+	int lf;
+
+	while ((n = getline(&line, &size, fp)) > 0) {
+		lf = n && line[n - 1] == '\n';
+		i = n -= lf;
+		for (n = 0; i--;) {
+			if ((line[i] & 0xC0) == 0x80) {
+				n++;
+			} else {
+				fwrite(line + i, 1, n + 1, stdout);
+				n = 0;
+			}
+		}
+		if (n)
+			fwrite(line, 1, n, stdout);
+		if (lf)
+			fputc('\n', stdout);
+	}
+}
+
+int
+main(int argc, char *argv[])
+{
+	FILE *fp;
+	int ret = 0;
+
+	ARGBEGIN {
+	default:
+		usage();
+	} ARGEND
+
+	if (!argc) {
+		rev(stdin);
+	} else {
+		for (; *argv; argc--, argv++) {
+			if (!strcmp(*argv, "-")) {
+				*argv = "<stdin>";
+				fp = stdin;
+			} else if (!(fp = fopen(*argv, "r"))) {
+				weprintf("fopen %s:", *argv);
+				ret = 1;
+				continue;
+			}
+			rev(fp);
+			if (fp != stdin && fshut(fp, *argv))
+				ret = 1;
+		}
+	}
+
+	ret |= fshut(stdin, "<stdin>") | fshut(stdout, "<stdout>");
+
+	return ret;
+}