diff --git a/src/cmd/fmt.c b/src/cmd/fmt.c
new file mode 100644
index 0000000..e43731e
--- /dev/null
+++ b/src/cmd/fmt.c
@@ -0,0 +1,241 @@
+#include <u.h>
+#include <libc.h>
+#include <bio.h>
+#include <ctype.h>
+
+/*
+ * block up paragraphs, possibly with indentation
+ */
+
+int extraindent = 0;		/* how many spaces to indent all lines */
+int indent = 0;			/* current value of indent, before extra indent */
+int length = 70;		/* how many columns per output line */
+int join = 1;			/* can lines be joined? */
+int maxtab = 8;
+Biobuf bin;
+Biobuf bout;
+
+typedef struct Word Word;
+struct Word{
+	int	bol;
+	int	indent;
+	char	text[1];
+};
+
+void	fmt(void);
+
+void
+usage(void)
+{
+	fprint(2, "usage: %s [-j] [-i indent] [-l length] [file...]\n", argv0);
+	exits("usage");
+}
+
+void
+main(int argc, char **argv)
+{
+	int i, f;
+	char *s, *err;
+
+	ARGBEGIN{
+	case 'i':
+		extraindent = atoi(EARGF(usage()));
+		break;
+	case 'j':
+		join = 0;
+		break;
+	case 'w':
+	case 'l':
+		length = atoi(EARGF(usage()));
+		break;
+	default:
+		usage();
+	}ARGEND
+
+	if(length <= indent){
+		fprint(2, "%s: line length<=indentation\n", argv0);
+		exits("length");
+	}
+
+	s=getenv("tabstop");
+	if(s!=nil && atoi(s)>0)
+		maxtab=atoi(s);
+	err = nil;
+	Binit(&bout, 1, OWRITE);
+	if(argc <= 0){
+		Binit(&bin, 0, OREAD);
+		fmt();
+	}else{
+		for(i=0; i<argc; i++){
+			f = open(argv[i], OREAD);
+			if(f < 0){
+				fprint(2, "%s: can't open %s: %r\n", argv0, argv[i]);
+				err = "open";
+			}else{
+				Binit(&bin, f, OREAD);
+				fmt();
+				Bterm(&bin);
+				if(i != argc-1)
+					Bputc(&bout, '\n');
+			}
+		}
+	}
+	exits(err);
+}
+
+int
+indentof(char **linep)
+{
+	int i, ind;
+	char *line;
+
+	ind = 0;
+	line = *linep;
+	for(i=0; line[i]; i++)
+		switch(line[i]){
+		default:
+			*linep = line;
+			return ind;
+		case ' ':
+			ind++;
+			break;
+		case '\t':
+			ind += maxtab;
+			ind -= ind%maxtab;
+			break;
+		}
+			
+	/* plain white space doesn't change the indent */
+	*linep = "";
+	return indent;
+}
+
+Word**
+addword(Word **words, int *nwordp, char *s, int l, int indent, int bol)
+{
+	Word *w;
+
+	w = malloc(sizeof(Word)+l+1);
+	memmove(w->text, s, l);
+	w->text[l] = '\0';
+	w->indent = indent;
+	w->bol = bol;
+	words = realloc(words, (*nwordp+1)*sizeof(Word*));
+	words[(*nwordp)++] = w;
+	return words;
+}
+
+Word**
+parseline(char *line, Word **words, int *nwordp)
+{
+	int ind, l, bol;
+
+	ind = indentof(&line);
+	indent = ind;
+	bol = 1;
+	for(;;){
+		/* find next word */
+		while(*line==' ' || *line=='\t')
+			line++;
+		if(*line == '\0'){
+			if(bol)
+				return addword(words, nwordp, "", 0, -1, bol);
+			break;
+		}
+		/* how long is this word? */
+		for(l=0; line[l]; l++)
+			if(line[l]==' ' || line[l]=='\t')
+				break;
+		words = addword(words, nwordp, line, l, indent, bol);
+		bol = 0;
+		line += l;
+	}
+	return words;
+}
+
+void
+printindent(int w)
+{
+	while(w >= maxtab){
+		Bputc(&bout, '\t');
+		w -= maxtab;
+	}
+	while(w > 0){
+		Bputc(&bout, ' ');
+		w--;
+	}
+}
+
+/* give extra space if word ends with period, etc. */
+int
+nspaceafter(char *s)
+{
+	int n;
+
+	n = strlen(s);
+	if(n < 2)
+		return 1;
+	if(isupper(s[0]) && n < 4)
+		return 1;
+	if(strchr(".!?", s[n-1]) != nil)
+		return 2;
+	return 1;
+}
+	
+
+void
+printwords(Word **w, int nw)
+{
+	int i, j, n, col, nsp;
+
+	/* one output line per loop */
+	for(i=0; i<nw; ){
+		/* if it's a blank line, print it */
+		if(w[i]->indent == -1){
+			Bputc(&bout, '\n');
+			if(++i == nw)	/* out of words */
+				break;
+		}
+		/* emit leading indent */
+		col = extraindent+w[i]->indent;
+		printindent(col);
+		/* emit words until overflow; always emit at least one word */
+		for(n=0;; n++){
+			Bprint(&bout, "%s", w[i]->text);
+			col += utflen(w[i]->text);
+			if(++i == nw)
+				break;	/* out of words */
+			if(w[i]->indent != w[i-1]->indent)
+				break;	/* indent change */
+			nsp = nspaceafter(w[i-1]->text);
+			if(col+nsp+utflen(w[i]->text) > extraindent+length)
+				break;	/* fold line */
+			if(!join && n != 0 && w[i]->bol)
+				break;
+			for(j=0; j<nsp; j++)
+				Bputc(&bout, ' ');	/* emit space; another word will follow */
+			col += nsp;
+		}
+		/* emit newline */
+		Bputc(&bout, '\n');
+	}
+}
+
+void
+fmt(void)
+{
+	char *s;
+	int i, nw;
+	Word **w;
+
+	nw = 0;
+	w = nil;
+	while((s = Brdstr(&bin, '\n', 1)) != nil){
+		w = parseline(s, w, &nw);
+		free(s);
+	}
+	printwords(w, nw);
+	for(i=0; i<nw; i++)
+		free(w[i]);
+	free(w);
+}