[PATCH] split: adding --exec, --exec-wait, and --pause

[Chris Frey]

Hi,

This is an initial rough draft of a patch to add exec and pause support to
the split command.

The basic idea is to let the user have some control of what happens to
each output file as it is created.  A command may be run (say burning
file chunks to CD), or split can pause for the user to press ENTER
after each output file is closed.

The new help options look like this:

  -e, --exec=CMD          run CMD after each output file is closed
  -w, --exec-wait=CMD     run CMD after each output file is closed
                          and wait for the child to exit
  -p, --pause             pause for keypress after each output file is closed

I'm not happy with the futzing around with the STDIN_FILENO, as both exec
and pause need to read from the user's terminal, not the data stream.
What I've done is check if STDOUT_FILENO is a tty, and if so, open() it.
This causes problems if you su to another user and your tty is owned
by the first user, but I'm not sure how to get around that.

This patch is in the public domain.

Let me know what you think,
- Chris


--- split.c     2005-09-14 08:00:12.000000000 -0400
+++ split-cdf01.c       2005-09-14 07:59:48.000000000 -0400
@@ -76,6 +76,17 @@
    output file is opened. */
 static bool verbose;
 
+/* If true, pause after each output file is closed, to let the user press
+   ENTER.  Use tty_pause_fd for the I/O.  */
+static bool pause_mode;
+static int tty_pause_fd;
+
+/* The user-specified command to run after each output file is closed.
+   Run it through sprintf first in order to place the latest output
+   filename in the command */
+static char *exec_command;
+static bool exec_wait;
+
 /* For long options that have no equivalent short option, use a
    non-character as a pseudo short option, starting with CHAR_MAX + 1.  */
 enum
@@ -91,6 +102,9 @@
   {"suffix-length", required_argument, NULL, 'a'},
   {"numeric-suffixes", no_argument, NULL, 'd'},
   {"verbose", no_argument, NULL, VERBOSE_OPTION},
+  {"pause", no_argument, NULL, 'p'},
+  {"exec", required_argument, NULL, 'e'},
+  {"exec-wait", required_argument, NULL, 'w'},
   {GETOPT_HELP_OPTION_DECL},
   {GETOPT_VERSION_OPTION_DECL},
   {NULL, 0, NULL, 0}
@@ -122,7 +136,11 @@
   -b, --bytes=SIZE        put SIZE bytes per output file\n\
   -C, --line-bytes=SIZE   put at most SIZE bytes of lines per output file\n\
   -d, --numeric-suffixes  use numeric suffixes instead of alphabetic\n\
+  -e, --exec=CMD          run CMD after each output file is closed\n\
+  -w, --exec-wait=CMD     run CMD after each output file is closed\n\
+                          and wait for the child to exit\n\
   -l, --lines=NUMBER      put NUMBER lines per output file\n\
+  -p, --pause             pause for keypress after each output file is 
closed\n\
 "), DEFAULT_SUFFIX_LENGTH);
       fputs (_("\
       --verbose           print a diagnostic to standard error just\n\
@@ -195,6 +213,81 @@
     }
 }
 
+
+static void
+run_exec_command (void)
+{
+  int child_pid = fork();
+  
+  if (child_pid == 0)
+    {
+      /* child process */
+      char *cmd_line;
+      char tty_name[100];
+      int stdin_fd;
+
+      /* close all data files */
+      close (STDIN_FILENO);
+      if (output_desc >= 0)
+        close (output_desc);
+      if (pause_mode)
+        close (tty_pause_fd);
+
+      /* recreate a stdin for the child */
+      if (ttyname_r(STDOUT_FILENO, tty_name, sizeof(tty_name)) != 0)
+       error (EXIT_FAILURE, errno, "can't discover tty name");
+      stdin_fd = open (tty_name, O_RDWR);
+      if (stdin_fd == -1)
+       error (EXIT_FAILURE, errno, "can't open tty for "
+               "pause prompting");
+      if (stdin_fd != STDIN_FILENO)
+        {
+         dup2 (stdin_fd, STDIN_FILENO);
+         close (stdin_fd);
+       }
+
+      /* build the command line, passing a few filenames so the user
+       * can use multiple %s if he needs to... the cheap way */
+      asprintf (&cmd_line, exec_command, outfile, outfile, outfile, outfile,
+               outfile, outfile, outfile);
+
+      /* exec it */
+      execl ("/bin/sh", "/bin/sh", "-c", cmd_line, NULL);
+
+      /* exit with failure if we get here */
+      exit (1);
+    }
+  else if (child_pid == -1)
+    {
+      /* parent process, child had problems */
+      error (EXIT_FAILURE, errno, "can't fork to exec command");
+    }
+  else
+    {
+      /* parent process, success */
+      if (exec_wait)
+       waitpid (child_pid, NULL, 0);
+    }
+}
+
+
+static void
+split_point (void)
+{
+  if (exec_command)
+    run_exec_command ();
+
+  if (pause_mode)
+    {
+      char nothing;
+      write(tty_pause_fd, "Press ENTER to continue with next split file\n"
+            "Just finished: ", 60);
+      write(tty_pause_fd, outfile, strlen(outfile));
+      read(tty_pause_fd, &nothing, 1);
+    }
+}
+
+
 /* Write BYTES bytes at BP to an output file.
    If NEW_FILE_FLAG is true, open the next output file.
    Otherwise add to the same output file already in use.  */
@@ -206,6 +299,8 @@
     {
       if (output_desc >= 0 && close (output_desc) < 0)
        error (EXIT_FAILURE, errno, "%s", outfile);
+      else if (output_desc >= 0)
+        split_point ();
 
       next_file_name ();
       if (verbose)
@@ -406,7 +501,7 @@
       /* This is the argv-index of the option we will read next.  */
       int this_optind = optind ? optind : 1;
 
-      c = getopt_long (argc, argv, "0123456789C:a:b:dl:", longopts, NULL);
+      c = getopt_long (argc, argv, "0123456789C:a:b:dl:pe:w:", longopts, NULL);
       if (c == -1)
        break;
 
@@ -494,6 +589,43 @@
          suffix_alphabet = "0123456789";
          break;
 
+       case 'p':
+         pause_mode = true;
+         if (isatty(STDOUT_FILENO))
+           {
+             /* we have a valid tty on stdout, let's try to open it for
+              * reading and writing (for the prompt), since stdin is
+              * being used for data */
+             char tty_name[100];
+             if (ttyname_r(STDOUT_FILENO, tty_name, sizeof(tty_name)) != 0)
+               error (EXIT_FAILURE, errno, "can't discover tty name");
+             tty_pause_fd = open (tty_name, O_RDWR);
+             if (tty_pause_fd == -1)
+               error (EXIT_FAILURE, errno, "can't open tty for "
+                       "pause prompting");
+           }
+         else
+           {
+             error (EXIT_FAILURE, 0, "stdout is not a tty, can't prompt"
+                    " on pause points");
+           }
+         break;
+
+       case 'e':
+       case 'w':
+         if (! exec_command)
+           {
+             size_t cmd_length = strlen(optarg);
+             exec_command = xmalloc (cmd_length + 1);
+             strcpy (exec_command, optarg);
+
+             if (c == 'w')
+               exec_wait = true;
+           }
+         else
+           error (EXIT_FAILURE, 0, "exec already specified!");
+         break;
+
        case VERBOSE_OPTION:
          verbose = true;
          break;
@@ -578,6 +710,8 @@
     error (EXIT_FAILURE, errno, "%s", infile);
   if (output_desc >= 0 && close (output_desc) < 0)
     error (EXIT_FAILURE, errno, "%s", outfile);
+  else if (output_desc >= 0)
+    split_point ();
 
   exit (EXIT_SUCCESS);
 }