sfdisk: add option to use maximum partition size

Based on patch from Alex Bligh <alex@alex.org.uk>, Alex wrote:

   By default, omitting a size parameter means that the maximum sized partition
   is used. However, this option is not available in conjunction with the -N
   flag, as under such circumstances the default is the current size of the
   partition. This patch allows a size to be specified as "+" in which case
   the maximum sized partition is used, irrespective of the setting of the -N
   flag.

   This allows partitions to be programatically resized to their maximum size,
   by (for instance):

     echo ",+," | sfdisk -N1 /dev/sda

   This is non-trivial to do without the patch, as -N makes the default size
   the existing size. As there is (without this patch) no way of reading the
   maximum size, the only option is to delete the partition and recreate it.
   This is undesirable for a number of reasons (e.g. errors between delete
   and recreate).

Addresses: https://bugs.launchpad.net/ubuntu/+source/util-linux/+bug/686124
Signed-off-by: Karel Zak <kzak@redhat.com>

diff --git a/fdisk/sfdisk.8 b/fdisk/sfdisk.8
index 7e2dca939a403c350a4e8c6ea575ea2280396972..f6e98c17f1ddc250ace0a408800b20da9bc98966 100644 (file)
--- a/fdisk/sfdisk.8
+++ b/fdisk/sfdisk.8
@@ -428,7 +428,9 @@ the defaults are: Linux partition, Extended partition, Empty, Empty.
 .LP
 But when the \-N option (change a single partition only) is given,
 the default for each field is its previous value.
-
+.LP
+A '+' can be specified instead of a number for size, which means
+as much as possible. This is useful with the \-N option.
 .SH EXAMPLE
 The command
 .RS

diff --git a/fdisk/sfdisk.c b/fdisk/sfdisk.c
index fd2f27eb133c93ab50d915c7b7bb07f1b852383d..958faaebfafb434a76295306e87012f8f05e4c85 100644 (file)
--- a/fdisk/sfdisk.c
+++ b/fdisk/sfdisk.c
@@ -2100,6 +2100,8 @@ read_line(int pno, struct part_desc *ep, char *dev, int interactive,
     def = orig ? orig->size : (pno > 4 && pct > 1) ? 0 : ml1;
     if (fno < 2 || !*(fields[1]))
       p.size = def;
+    else if (!strcmp(fields[1], "+"))
+      p.size = ml1;
     else {
        if (get_ul(fields[1], &ul, def / unitsize(0), 0))
          return 0;