new utilities.
the .C files compile but are renamed to avoid building automatically.
diff --git a/src/cmd/idiff.c b/src/cmd/idiff.c
new file mode 100644
index 0000000..4732678
--- /dev/null
+++ b/src/cmd/idiff.c
@@ -0,0 +1,335 @@
+/*
+ * interactive diff, inspired/stolen from
+ * kernighan and pike, _unix programming environment_.
+ */
+
+#include <u.h>
+#include <libc.h>
+#include <bio.h>
+
+int diffbflag;
+int diffwflag;
+
+void copy(Biobuf*, char*, Biobuf*, char*);
+void idiff(Biobuf*, char*, Biobuf*, char*, Biobuf*, char*, Biobuf*, char*);
+int opentemp(char*, int, long);
+void rundiff(char*, char*, int);
+
+void
+usage(void)
+{
+ fprint(2, "usage: idiff [-bw] file1 file2\n");
+ exits("usage");
+}
+
+void
+main(int argc, char **argv)
+{
+ int fd, ofd;
+ char diffout[40], idiffout[40];
+ Biobuf *b1, *b2, bdiff, bout, bstdout;
+ Dir *d;
+
+ ARGBEGIN{
+ default:
+ usage();
+ case 'b':
+ diffbflag++;
+ break;
+ case 'w':
+ diffwflag++;
+ break;
+ }ARGEND
+
+ if(argc != 2)
+ usage();
+
+ if((d = dirstat(argv[0])) == nil)
+ sysfatal("stat %s: %r", argv[0]);
+ if(d->mode&DMDIR)
+ sysfatal("%s is a directory", argv[0]);
+ free(d);
+ if((d = dirstat(argv[1])) == nil)
+ sysfatal("stat %s: %r", argv[1]);
+ if(d->mode&DMDIR)
+ sysfatal("%s is a directory", argv[1]);
+ free(d);
+
+ if((b1 = Bopen(argv[0], OREAD)) == nil)
+ sysfatal("open %s: %r", argv[0]);
+ if((b2 = Bopen(argv[1], OREAD)) == nil)
+ sysfatal("open %s: %r", argv[1]);
+
+ strcpy(diffout, "/tmp/idiff.XXXXXX");
+ fd = opentemp(diffout, ORDWR|ORCLOSE, 0);
+ strcpy(idiffout, "/tmp/idiff.XXXXXX");
+ ofd = opentemp(idiffout, ORDWR|ORCLOSE, 0);
+ rundiff(argv[0], argv[1], fd);
+ seek(fd, 0, 0);
+ Binit(&bdiff, fd, OREAD);
+ Binit(&bout, ofd, OWRITE);
+ idiff(b1, argv[0], b2, argv[1], &bdiff, diffout, &bout, idiffout);
+ Bterm(&bdiff);
+ Bflush(&bout);
+ seek(ofd, 0, 0);
+ Binit(&bout, ofd, OREAD);
+ Binit(&bstdout, 1, OWRITE);
+ copy(&bout, idiffout, &bstdout, "<stdout>");
+ exits(nil);
+}
+
+int
+opentemp(char *template, int mode, long perm)
+{
+ int fd, i;
+ char *p;
+
+ p = strdup(template);
+ if(p == nil)
+ sysfatal("strdup out of memory");
+ fd = -1;
+ for(i=0; i<10; i++){
+ mktemp(p);
+ if(access(p, 0) < 0 && (fd=create(p, mode, perm)) >= 0)
+ break;
+ strcpy(p, template);
+ }
+ if(fd < 0)
+ sysfatal("could not create temporary file");
+ strcpy(template, p);
+ free(p);
+
+ return fd;
+}
+
+void
+rundiff(char *arg1, char *arg2, int outfd)
+{
+ char *arg[10], *p;
+ int narg, pid;
+ Waitmsg *w;
+
+ narg = 0;
+ arg[narg++] = "/bin/diff";
+ arg[narg++] = "-n";
+ if(diffbflag)
+ arg[narg++] = "-b";
+ if(diffwflag)
+ arg[narg++] = "-w";
+ arg[narg++] = arg1;
+ arg[narg++] = arg2;
+ arg[narg] = nil;
+
+ switch(pid = fork()){
+ case -1:
+ sysfatal("fork: %r");
+
+ case 0:
+ dup(outfd, 1);
+ close(0);
+ exec("/bin/diff", arg);
+ sysfatal("exec: %r");
+
+ default:
+ w = wait();
+ if(w==nil)
+ sysfatal("wait: %r");
+ if(w->pid != pid)
+ sysfatal("wait got unexpected pid %d", w->pid);
+ if((p = strchr(w->msg, ':')) && strcmp(p, ": some") != 0)
+ sysfatal("%s", w->msg);
+ free(w);
+ }
+}
+
+void
+runcmd(char *cmd)
+{
+ char *arg[10];
+ int narg, pid, wpid;
+
+ narg = 0;
+ arg[narg++] = "/bin/rc";
+ arg[narg++] = "-c";
+ arg[narg++] = cmd;
+ arg[narg] = nil;
+
+ switch(pid = fork()){
+ case -1:
+ sysfatal("fork: %r");
+
+ case 0:
+ exec("/bin/rc", arg);
+ sysfatal("exec: %r");
+
+ default:
+ wpid = waitpid();
+ if(wpid < 0)
+ sysfatal("wait: %r");
+ if(wpid != pid)
+ sysfatal("wait got unexpected pid %d", wpid);
+ }
+}
+
+void
+parse(char *s, int *pfrom1, int *pto1, int *pcmd, int *pfrom2, int *pto2)
+{
+ *pfrom1 = *pto1 = *pfrom2 = *pto2 = 0;
+
+ s = strchr(s, ':');
+ if(s == nil)
+ sysfatal("bad diff output0");
+ s++;
+ *pfrom1 = strtol(s, &s, 10);
+ if(*s == ','){
+ s++;
+ *pto1 = strtol(s, &s, 10);
+ }else
+ *pto1 = *pfrom1;
+ if(*s++ != ' ')
+ sysfatal("bad diff output1");
+ *pcmd = *s++;
+ if(*s++ != ' ')
+ sysfatal("bad diff output2");
+ s = strchr(s, ':');
+ if(s == nil)
+ sysfatal("bad diff output3");
+ s++;
+ *pfrom2 = strtol(s, &s, 10);
+ if(*s == ','){
+ s++;
+ *pto2 = strtol(s, &s, 10);
+ }else
+ *pto2 = *pfrom2;
+}
+
+void
+skiplines(Biobuf *b, char *name, int n)
+{
+ int i;
+
+ for(i=0; i<n; i++){
+ while(Brdline(b, '\n')==nil){
+ if(Blinelen(b) <= 0)
+ sysfatal("early end of file on %s", name);
+ Bseek(b, Blinelen(b), 1);
+ }
+ }
+}
+
+void
+copylines(Biobuf *bin, char *nin, Biobuf *bout, char *nout, int n)
+{
+ char buf[4096], *p;
+ int i, m;
+
+ for(i=0; i<n; i++){
+ while((p=Brdline(bin, '\n'))==nil){
+ if(Blinelen(bin) <= 0)
+ sysfatal("early end of file on %s", nin);
+ m = Blinelen(bin);
+ if(m > sizeof buf)
+ m = sizeof buf;
+ m = Bread(bin, buf, m);
+ if(Bwrite(bout, buf, m) != m)
+ sysfatal("error writing %s: %r", nout);
+ }
+ if(Bwrite(bout, p, Blinelen(bin)) != Blinelen(bin))
+ sysfatal("error writing %s: %r", nout);
+ }
+}
+
+void
+copy(Biobuf *bin, char *nin, Biobuf *bout, char *nout)
+{
+ char buf[4096];
+ int m;
+
+ USED(nin);
+ while((m = Bread(bin, buf, sizeof buf)) > 0)
+ if(Bwrite(bout, buf, m) != m)
+ sysfatal("error writing %s: %r", nout);
+}
+
+void
+idiff(Biobuf *b1, char *name1, Biobuf *b2, char *name2, Biobuf *bdiff, char *namediff, Biobuf *bout, char *nameout)
+{
+ char buf[256], *p;
+ int interactive, defaultanswer, cmd, diffoffset;
+ int n, from1, to1, from2, to2, nf1, nf2;
+ Biobuf berr;
+
+ nf1 = 1;
+ nf2 = 1;
+ interactive = 1;
+ defaultanswer = 0;
+ Binit(&berr, 2, OWRITE);
+ while(diffoffset = Boffset(bdiff), p = Brdline(bdiff, '\n')){
+ p[Blinelen(bdiff)-1] = '\0';
+ parse(p, &from1, &to1, &cmd, &from2, &to2);
+ p[Blinelen(bdiff)-1] = '\n';
+ n = to1-from1 + to2-from2 + 1; /* #lines from diff */
+ if(cmd == 'c')
+ n += 2;
+ else if(cmd == 'a')
+ from1++;
+ else if(cmd == 'd')
+ from2++;
+ to1++; /* make half-open intervals */
+ to2++;
+ if(interactive){
+ p[Blinelen(bdiff)-1] = '\0';
+ fprint(2, "%s\n", p);
+ p[Blinelen(bdiff)-1] = '\n';
+ copylines(bdiff, namediff, &berr, "<stderr>", n);
+ Bflush(&berr);
+ }else
+ skiplines(bdiff, namediff, n);
+ do{
+ if(interactive){
+ fprint(2, "? ");
+ memset(buf, 0, sizeof buf);
+ if(read(0, buf, sizeof buf - 1) < 0)
+ sysfatal("read console: %r");
+ }else
+ buf[0] = defaultanswer;
+
+ switch(buf[0]){
+ case '>':
+ copylines(b1, name1, bout, nameout, from1-nf1);
+ skiplines(b1, name1, to1-from1);
+ skiplines(b2, name2, from2-nf2);
+ copylines(b2, name2, bout, nameout, to2-from2);
+ break;
+ case '<':
+ copylines(b1, name1, bout, nameout, to1-nf1);
+ skiplines(b2, name2, to2-nf2);
+ break;
+ case '=':
+ copylines(b1, name1, bout, nameout, from1-nf1);
+ skiplines(b1, name1, to1-from1);
+ skiplines(b2, name2, to2-nf2);
+ if(Bseek(bdiff, diffoffset, 0) != diffoffset)
+ sysfatal("seek in diff output: %r");
+ copylines(bdiff, namediff, bout, nameout, n+1);
+ break;
+ case '!':
+ runcmd(buf+1);
+ break;
+ case 'q':
+ if(buf[1]=='<' || buf[1]=='>' || buf[1]=='='){
+ interactive = 0;
+ defaultanswer = buf[1];
+ }else
+ fprint(2, "must be q<, q>, or q=\n");
+ break;
+ default:
+ fprint(2, "expect: <, >, =, q<, q>, q=, !cmd\n");
+ break;
+ }
+ }while(buf[0] != '<' && buf[0] != '>' && buf[0] != '=');
+ nf1 = to1;
+ nf2 = to2;
+ }
+ copy(b1, name1, bout, nameout);
+}
