new utilities.
the .C files compile but are renamed to avoid building automatically.
diff --git a/src/cmd/comm.c b/src/cmd/comm.c
new file mode 100644
index 0000000..8109c59
--- /dev/null
+++ b/src/cmd/comm.c
@@ -0,0 +1,178 @@
+#include <u.h>
+#include <libc.h>
+#include <bio.h>
+
+#define LB 2048
+int one;
+int two;
+int three;
+
+char *ldr[3];
+
+Biobuf *ib1;
+Biobuf *ib2;
+Biobuf *openfil(char*);
+int rd(Biobuf*, char*);
+void wr(char*, int);
+void copy(Biobuf*, char*, int);
+int compare(char*, char*);
+
+void
+main(int argc, char *argv[])
+{
+ int l;
+ char lb1[LB],lb2[LB];
+
+ ldr[0] = "";
+ ldr[1] = "\t";
+ ldr[2] = "\t\t";
+ l = 2;
+ ARGBEGIN{
+ case '1':
+ if(!one) {
+ one = 1;
+ ldr[1][0] =
+ ldr[2][l--] = '\0';
+ }
+ break;
+
+ case '2':
+ if(!two) {
+ two = 1;
+ ldr[2][l--] = '\0';
+ }
+ break;
+
+ case '3':
+ three = 1;
+ break;
+
+ default:
+ goto Usage;
+
+ }ARGEND
+
+ if(argc < 2) {
+ Usage:
+ fprint(2, "usage: comm [-123] file1 file2\n");
+ exits("usage");
+ }
+
+ ib1 = openfil(argv[0]);
+ ib2 = openfil(argv[1]);
+
+
+ if(rd(ib1,lb1) < 0){
+ if(rd(ib2,lb2) < 0)
+ exits(0);
+ copy(ib2,lb2,2);
+ }
+ if(rd(ib2,lb2) < 0)
+ copy(ib1,lb1,1);
+
+ for(;;){
+ switch(compare(lb1,lb2)) {
+ case 0:
+ wr(lb1,3);
+ if(rd(ib1,lb1) < 0) {
+ if(rd(ib2,lb2) < 0)
+ exits(0);
+ copy(ib2,lb2,2);
+ }
+ if(rd(ib2,lb2) < 0)
+ copy(ib1,lb1,1);
+ continue;
+
+ case 1:
+ wr(lb1,1);
+ if(rd(ib1,lb1) < 0)
+ copy(ib2,lb2,2);
+ continue;
+
+ case 2:
+ wr(lb2,2);
+ if(rd(ib2,lb2) < 0)
+ copy(ib1,lb1,1);
+ continue;
+ }
+ }
+ exits(0);
+}
+
+int
+rd(Biobuf *file, char *buf)
+{
+ int i, c;
+
+ i = 0;
+ while((c = Bgetc(file)) != Beof) {
+ *buf = c;
+ if(c == '\n' || i > LB-2) {
+ *buf = '\0';
+ return 0;
+ }
+ i++;
+ buf++;
+ }
+ return -1;
+}
+
+void
+wr(char *str, int n)
+{
+
+ switch(n){
+ case 1:
+ if(one)
+ return;
+ break;
+
+ case 2:
+ if(two)
+ return;
+ break;
+
+ case 3:
+ if(three)
+ return;
+ }
+ print("%s%s\n", ldr[n-1],str);
+}
+
+void
+copy(Biobuf *ibuf, char *lbuf, int n)
+{
+ do
+ wr(lbuf,n);
+ while(rd(ibuf,lbuf) >= 0);
+ exits(0);
+}
+
+int
+compare(char *a, char *b)
+{
+ while(*a == *b){
+ if(*a == '\0')
+ return 0;
+ a++;
+ b++;
+ }
+ if(*a < *b)
+ return 1;
+ return 2;
+}
+
+Biobuf*
+openfil(char *s)
+{
+ Biobuf *b;
+
+ if(s[0]=='-' && s[1]==0)
+ s = "/fd/0";
+ b = Bopen(s, OREAD);
+ if(b)
+ return b;
+ fprint(2,"comm: cannot open %s: %r\n",s);
+ exits("open");
+ return 0; /* shut up ken */
+}
