Author: <hesso@pool.math.tu-berlin.de>
Description: Add lookup code for the creation time of each session. Requires
digging in /proc/$pid and /proc/uptime, though, so it's definitely
no candidate for the Beautiful C contest.
Affects screen's behaviour in the following situations:
* 'screen -ls' lists available sessions sorted chronologically
* 'screen -RR' now picks the youngest session instead of an
arbitrary one
Index: screen/doc/screen.1
===================================================================
--- screen.orig/doc/screen.1	2014-04-28 03:17:56.464112915 +0200
+++ screen/doc/screen.1	2014-04-28 03:17:56.448112764 +0200
@@ -244,7 +244,7 @@
 .IR screen ,
 but prints a list of
 .I pid.tty.host
-strings identifying your
+strings and creation timestamps identifying your
 .I screen
 sessions.
 Sessions marked `detached' can be resumed with \*Qscreen \-r\*U. Those marked
@@ -342,7 +342,7 @@
 sessions in another user's directory. This requires setuid-root.
 .TP 5
 .B \-R
-attempts to resume the first detached
+attempts to resume the youngest (in terms of creation time) detached
 .I screen
 session it finds.  If successful, all other command-line options are ignored.
 If no detached session exists, starts a new session using the specified
@@ -352,6 +352,8 @@
 .I screen
 is run as a login-shell (actually screen uses \*Q\-xRR\*U in that case).
 For combinations with the \fB\-d\fP/\fB\-D\fP option see there.
+.B Note:
+Time-based session selection is a Debian addition.
 .TP 5
 .BI "\-s " program 
 sets the default shell to the program specified, instead of the value
Index: screen/doc/screen.texinfo
===================================================================
--- screen.orig/doc/screen.texinfo	2014-04-28 03:17:56.464112915 +0200
+++ screen/doc/screen.texinfo	2014-04-28 03:17:56.452112800 +0200
@@ -320,7 +320,8 @@
 @itemx -list [@var{match}]
 Do not start @code{screen}, but instead print a list of session
 identification strings (usually of the form @var{pid.tty.host};
-@pxref{Session Name}).  Sessions marked @samp{detached} can be resumed
+@pxref{Session Name}) and the corresponding creation timestamps.
+Sessions marked @samp{detached} can be resumed
 with @code{screen -r}.  Those marked @samp{attached} are running and
 have a controlling terminal.  If the session runs in multiuser mode,
 it is marked @samp{multi}.  Sessions marked as @samp{unreachable} either
@@ -406,14 +407,15 @@
 sessions in another user's directory. This requires setuid-root.
 
 @item -R
-Resume the first appropriate detached @code{screen} session.  If
-successful, all other command-line options are ignored.  If no detached
+Resume the most-recently created appropriate detached @code{screen} session.
+If successful, all other command-line options are ignored.  If no detached
 session exists, start a new session using the specified options, just as
 if @samp{-R} had not been specified.  This option is set by default if
 screen is run as a login-shell (actually screen uses @samp{-xRR} in
 that case).
 For combinations with the 
 @samp{-D}/@samp{-d} option see there.
+@samp{Note:} Time-based session selection is a Debian addition.
 
 @item -s @var{program}
 Set the default shell to be @var{program}.  By default, @code{screen}
Index: screen/extern.h
===================================================================
--- screen.orig/extern.h	2014-04-28 03:17:56.464112915 +0200
+++ screen/extern.h	2014-04-28 03:17:56.456112845 +0200
@@ -390,6 +390,8 @@
 #else
 extern int   xsnprintf __P(());
 #endif
+extern time_t SessionCreationTime __P((const char *));
+extern time_t GetUptime __P((void));
 
 
 /* acl.c */
Index: screen/misc.c
===================================================================
--- screen.orig/misc.c	2014-04-28 03:17:56.464112915 +0200
+++ screen/misc.c	2014-04-28 03:17:56.456112845 +0200
@@ -29,6 +29,7 @@
 #include <sys/types.h>
 #include <sys/stat.h>	/* mkdir() declaration */
 #include <signal.h>
+#include <fcntl.h>
 
 #include "config.h"
 #include "screen.h"
@@ -769,3 +770,40 @@
 }
 
 #endif
+
+time_t SessionCreationTime(const char *fifo) {
+  char ppath[20];
+  int pfd;
+  char pdata[512];
+  char *jiffies;
+
+  int pid = atoi(fifo);
+  if (pid <= 0) return 0;
+  sprintf(ppath, "/proc/%u/stat", pid);
+  pfd = open(ppath, O_RDONLY);
+  if (pfd < 0) return 0;
+  while (1) {
+    int R=0, RR;
+    RR = read(pfd, pdata + R, 512-R);
+    if (RR < 0) {close(pfd); return 0;}
+    else if (RR == 0) break;
+  }
+  close(pfd);
+
+  for (pfd=21, jiffies=pdata; pfd; --pfd) {
+    jiffies = strchr(jiffies, ' ');
+    if (!jiffies) break; else ++jiffies;
+  }
+  if (!jiffies) return 0;
+
+  return atol(jiffies) / 100;
+}
+
+time_t GetUptime(void) {
+  char uptimestr[32];
+  int fd = open("/proc/uptime", O_RDONLY);
+  if (fd < 0) return 0;
+  (void)read(fd, uptimestr, 32);
+  close(fd);
+  return atol(uptimestr);
+}
Index: screen/socket.c
===================================================================
--- screen.orig/socket.c	2014-04-28 03:17:56.464112915 +0200
+++ screen/socket.c	2014-04-28 03:17:56.456112845 +0200
@@ -125,16 +125,18 @@
   int sdirlen;
   int  matchlen = 0;
   char *name, *n;
-  int firsts = -1, sockfd;
-  char *firstn = NULL;
+  int sockfd = -1;
   int nfound = 0, ngood = 0, ndead = 0, nwipe = 0, npriv = 0;
   int nperfect = 0;
+  time_t sysboot = time(NULL) - GetUptime();
   struct sent
     {
       struct sent *next;
       int mode;
       char *name;
-    } *slist, **slisttail, *sent, *nsent;
+      time_t created;
+      int good;
+    } *slist, **slisttail, *sent, *nsent, *schosen = NULL;
 
   if (match)
     {
@@ -161,7 +163,6 @@
     Panic(errno, "Cannot opendir %s", SockPath);
 
   slist = 0;
-  slisttail = &slist;
   while ((dp = readdir(dirp)))
     {
       int cmatch = 0;
@@ -173,7 +174,7 @@
 	{
 	  n = name;
 	  /* if we don't want to match digits. Skip them */
-	  if ((*match <= '0' || *match > '9') && (*n > '0' && *n <= '9'))
+	  if ((*match < '0' || *match > '9') && (*n >= '0' && *n <= '9'))
 	    {
 	      while (*n >= '0' && *n <= '9')
 		n++;
@@ -252,12 +253,24 @@
       debug("  store it.\n");
       if ((sent = (struct sent *)malloc(sizeof(struct sent))) == 0)
 	continue;
-      sent->next = 0;
       sent->name = SaveStr(name);
       sent->mode = mode;
+      sent->created = sysboot + SessionCreationTime(name);
+      sent->good = 0;
+
+      for (slisttail = &slist; *slisttail; slisttail = &((*slisttail)->next))
+	{
+	  if ((*slisttail)->created < sent->created) break;
+	}
+
+      sent->next = *slisttail;
       *slisttail = sent;
-      slisttail = &sent->next;
       nfound++;
+      if (sockfd >= 0)
+	{
+	  close(sockfd);
+	  sockfd = -1;
+	}
       sockfd = MakeClientSocket(0);
 #ifdef USE_SETEUID
       /* MakeClientSocket sets ids back to eff */
@@ -316,6 +329,7 @@
 	  (!dflag && !rflag && !xflag))
 	{
 	  close(sockfd);
+	  sockfd = -1;
 	  debug("  no!\n");
 	  npriv++;		/* a good socket that was not for us */
 	  continue;
@@ -323,19 +337,8 @@
       ngood++;
       if (cmatch)
 	nperfect++;
-      if (fdp && (firsts == -1 || (cmatch && nperfect == 1)))
-	{
-	  if (firsts != -1)
-	    close(firsts);
-	  firsts = sockfd;
-	  firstn = sent->name;
-	  debug("  taken.\n");
-	}
-      else
-        {
-	  debug("  discarded.\n");
-	  close(sockfd);
-	}
+      sent->good = 1;
+      debug("  added to list.\n");
     }
   (void)closedir(dirp);
   if (!lsflag && nperfect == 1)
@@ -356,34 +359,42 @@
 	}
       for (sent = slist; sent; sent = sent->next)
 	{
+	  char timestr[64];
+	  if (sent->created == 0)
+	    {
+	      sprintf(timestr, "???");
+	    } else {
+	      strftime(timestr, 64, "%x %X", localtime(&sent->created));
+	    }
+	  printf("\t%s\t(%s)", sent->name, timestr);
 	  switch (sent->mode)
 	    {
 	    case 0700:
-	      printf("\t%s\t(Attached)\n", sent->name);
+	      printf("\t(Attached)\n");
 	      break;
 	    case 0600:
-	      printf("\t%s\t(Detached)\n", sent->name);
+	      printf("\t(Detached)\n");
 	      break;
 #ifdef MULTIUSER
 	    case 0701:
-	      printf("\t%s\t(Multi, attached)\n", sent->name);
+	      printf("\t(Multi, attached)\n");
 	      break;
 	    case 0601:
-	      printf("\t%s\t(Multi, detached)\n", sent->name);
+	      printf("\t(Multi, detached)\n");
 	      break;
 #endif
 	    case -1:
 	      /* No trigraphs here! */
-	      printf("\t%s\t(Dead ?%c?)\n", sent->name, '?');
+	      printf("\t(Dead ?%c?)\n", '?');
 	      break;
 	    case -2:
-	      printf("\t%s\t(Removed)\n", sent->name);
+	      printf("\t(Removed)\n");
 	      break;
 	    case -3:
-	      printf("\t%s\t(Remote or dead)\n", sent->name);
+	      printf("\t(Remote or dead)\n");
 	      break;
 	    case -4:
-	      printf("\t%s\t(Private)\n", sent->name);
+	      printf("\t(Private)\n");
 	      break;
 	    }
 	}
@@ -396,13 +407,37 @@
       else
         Msg(0, m, ndead > 1 ? "s" : "", ndead > 1 ? "" : "es");	/* other args for nethack */
     }
-  if (firsts != -1)
+  for (sent = slist; sent; sent = sent->next)
     {
-      sprintf(SockPath + sdirlen, "/%s", firstn);
-      *fdp = firsts;
+      if (sent->good)
+	{
+	  schosen = sent;
+	  break;
+	}
+    }
+  if (schosen && fdp)
+    {
+      if (sockfd >= 0 && !strcmp(SockPath + sdirlen + 1, schosen->name))
+	{
+	  *fdp = sockfd;
+	  sockfd = -1;
+	}
+      else
+	{
+	  sprintf(SockPath + sdirlen, "/%s", schosen->name);
+	  *fdp = MakeClientSocket(0);
+#ifdef USE_SETEUID
+	  xseteuid(real_uid);
+	  xsetegid(real_gid);
+#endif
+	}
     }
   else
     SockPath[sdirlen] = 0;
+  if (sockfd >= 0)
+    {
+      close(sockfd);
+    }
   for (sent = slist; sent; sent = nsent)
     {
       nsent = sent->next;