ref: 743124504e1558d594b2d9a3d0d329cc540435ed
author: kvik <[email protected]>
date: Tue Nov 17 02:41:34 EST 2020
init
--- /dev/null
+++ b/mkfile
@@ -1,0 +1,10 @@
+</$objtype/mkfile
+
+TARG=union
+OFILES=union.$O
+BIN=/$objtype/bin
+
+</sys/src/cmd/mkone
+
+uninstall:V:
+ rm -f $BIN/$TARG
--- /dev/null
+++ b/union.c
@@ -1,0 +1,121 @@
+#include <u.h>
+#include <libc.h>
+
+int fatal = 1;
+
+void
+usage(void)
+{+ fprint(2, "%s: [-abcr] path [...] mtpt\n", argv0);
+ exits("usage");+}
+
+void
+error(char *fmt, ...)
+{+ va_list arg;
+
+ va_start(arg, fmt);
+ vfprint(2, fmt, arg);
+ va_end(arg);
+ if(fatal)
+ exits("fatal");+}
+
+int
+same(char *p, char *q)
+{+ int r;
+ Dir *dp, *dq;
+
+ r = 0;
+ if((dp = dirstat(p)) == nil)
+ error("dirstat: %r\n");+ if((dq = dirstat(q)) == nil)
+ error("dirstat: %r\n");+ if(dp->type==dq->type
+ && dp->dev==dq->dev
+ && dp->qid.path==dq->qid.path
+ && dp->qid.vers==dq->qid.vers
+ && dp->qid.type==dq->qid.type)
+ r = 1;
+ free(dp);
+ free(dq);
+ return r;
+}
+
+void
+replace(char *p, char *q)
+{+ if((bind(p, q, MREPL)) < 0)
+ error("bind %s %s: %r\n", p, q);+}
+
+void
+after(char *p, char *q)
+{+ int fd;
+ long n;
+ char np[1024], nq[1024];
+ Dir *dir, *d;
+
+ if(same(p, q) == 0)
+ if((bind(p, q, MAFTER)) < 0)
+ error("bind %s %s: %r\n", p, q);+ if((fd = open(p, OREAD)) < 0)
+ sysfatal("open: %r");+ if((n = dirreadall(fd, &dir)) < 0)
+ error("dirreadall: %r\n");+ close(fd);
+ for(d = dir; n > 0; n--, d++){+ if((d->mode&DMDIR) == 0)
+ continue;
+ snprint(np, sizeof np, "%s/%s", p, d->name);
+ snprint(nq, sizeof nq, "%s/%s", q, d->name);
+ after(np, nq);
+ }
+}
+
+void
+before(char *p, char *q)
+{+ char *t;
+
+ t = "/mnt/temp";
+ replace(p, t);
+ after(q, t);
+ replace(t, q);
+ unmount(nil, t);
+}
+
+void
+main(int argc, char *argv[])
+{+ int i;
+ char *mtpt;
+ int op;
+
+ enum {After, Before, Replace};+ op = After;
+ ARGBEGIN{+ default: usage();
+ case 'a': op = After; break;
+ case 'b': op = Before; break;
+ case 'r': op = Replace; break;
+ case 'q': fatal = 0; break;
+ }ARGEND;
+ if(argc < 2)
+ usage();
+
+ mtpt = argv[argc-1];
+ for(i = 0; i < argc-1; i++)
+ switch(op){+ default: usage();
+ case After:
+ after(argv[i], mtpt); break;
+ case Before:
+ before(argv[i], mtpt); break;
+ case Replace:
+ replace(argv[i], mtpt); break;
+ }
+}