feature requests: trunc and maybe cmddiff

[Rafal Maszkowski]

I wonder if a wrapper around the system trunc(3) call could be included
into coreutils. It could be a separate command like:

        trunc my_file 234M

(I have made such for myself) or maybe an extension to the  touch
comand syntax. The command can shorten an existing file or create a
sparse new file.

If you do not like it in coreutils I CC to the moreutils author.


There is another command (script) I created some 10 years ago and I used
to use it frequently. The main purpose of it is estimating the ending
time of big and slow file copying. It can base the estimate on a number
contained in some row and field of e.g.  du  or  df  output. The output
of the traced command is saved every time  cmddiff  is called. The
output is kept in an RCS file in $HOME. The consecutive runs of  cmddiff
can check different fields of the same traced command. This one is
probably more suitable for moreutils.

address@hidden:/tmp,0# cmddiff -h
cmddiff - command output tracer

example:
cmddiff -f 2 -e 137000 -p -r 1.6 'wc -l addr.resolved'
-f 1          compare 1st field in 1st line; general form: line.field
-e 137000     calculate when the field is going to reach this value
-p            do not append path to the characteristic command string
-r 1.6        compare with revision 1.6, default: 0 == 1.1, -1 means the 
previous one
'wc ...'      the command

Somewhat artificial example:

Just df, not estimating anything yet:

address@hidden:/tmp,0# cmddiff df
first version:
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/sda1               489992    360999    103693  78% /
/dev/mapper/sys-tmp    2031440     68908   1857676   4% /tmp
/dev/mapper/sys-var    8125880   5016364   2690100  66% /var
/dev/mapper/sys-usr    5078656   1357396   3459116  29% /usr
/dev/mapper/sys-home  11173104   8909572   1686908  85% /home
/dev/mapper/sys-www   75164744  60372928  10912776  85% /www
tmpfs                  1037824         0   1037824   0% /dev/shm
tmpfs                    16384         0     16384   0% /var/spool/MIMEDefang
sunsite:/local/majordomo/lists
                       6196236   4916832   1217440  81% /sunsite/majordomo/lists
sunsite:/recesja     123378104  42310704  81067400  35% /www2

The RCS file:

address@hidden:/tmp,0# lt ~/.cmddiff/
total 2
-r--r--r-- 1 root root 920 Mar 10 13:11 f1eddd11eb190a1271fde939bfc86883,v

df again, still no options used:

address@hidden:/tmp,0# cmddiff df
df
--- f1eddd11eb190a1271fde939bfc86883    2009/03/10 12:11:45     1.1
+++ f1eddd11eb190a1271fde939bfc86883    2009/03/10 12:11:52
@@ -1,7 +1,7 @@
 Filesystem           1K-blocks      Used Available Use% Mounted on
-/dev/sda1               489992    360999    103693  78% /
+/dev/sda1               489992    361000    103692  78% /
 /dev/mapper/sys-tmp    2031440     68908   1857676   4% /tmp
-/dev/mapper/sys-var    8125880   5016364   2690100  66% /var
+/dev/mapper/sys-var    8125880   5016372   2690092  66% /var
 /dev/mapper/sys-usr    5078656   1357396   3459116  29% /usr
 /dev/mapper/sys-home  11173104   8909572   1686908  85% /home
 /dev/mapper/sys-www   75164744  60372928  10912776  85% /www

Now we would like to see when there will be 0 KB available in /var if it
is used at current speed (beginning from the first cmddif use):

address@hidden:/tmp,0# cmddiff -f 4.4 -e 0 df
df
--- f1eddd11eb190a1271fde939bfc86883    2009/03/10 12:11:45     1.1
+++ f1eddd11eb190a1271fde939bfc86883    2009/03/10 12:12:50
@@ -1,7 +1,7 @@
 Filesystem           1K-blocks      Used Available Use% Mounted on
-/dev/sda1               489992    360999    103693  78% /
+/dev/sda1               489992    361001    103691  78% /
 /dev/mapper/sys-tmp    2031440     68908   1857676   4% /tmp
-/dev/mapper/sys-var    8125880   5016364   2690100  66% /var
+/dev/mapper/sys-var    8125880   5016412   2690052  66% /var
 /dev/mapper/sys-usr    5078656   1357396   3459116  29% /usr
 /dev/mapper/sys-home  11173104   8909572   1686908  85% /home
 /dev/mapper/sys-www   75164744  60372928  10912776  85% /www
change: -.73846153846153846153 per second, ends: Tue Apr 21 18:05:49 MEST 2009

After few minutes the estimate is more precise:

address@hidden:/tmp,0# cmddiff -f 4.4 -e 0 df
df
--- f1eddd11eb190a1271fde939bfc86883    2009/03/10 12:11:45     1.1
+++ f1eddd11eb190a1271fde939bfc86883    2009/03/10 12:17:10
@@ -1,12 +1,12 @@
 Filesystem           1K-blocks      Used Available Use% Mounted on
-/dev/sda1               489992    360999    103693  78% /
+/dev/sda1               489992    361001    103691  78% /
 /dev/mapper/sys-tmp    2031440     68908   1857676   4% /tmp
-/dev/mapper/sys-var    8125880   5016364   2690100  66% /var
+/dev/mapper/sys-var    8125880   5016948   2689516  66% /var
 /dev/mapper/sys-usr    5078656   1357396   3459116  29% /usr
-/dev/mapper/sys-home  11173104   8909572   1686908  85% /home
-/dev/mapper/sys-www   75164744  60372928  10912776  85% /www
+/dev/mapper/sys-home  11173104   8909556   1686924  85% /home
+/dev/mapper/sys-www   75164744  60376004  10909700  85% /www
 tmpfs                  1037824         0   1037824   0% /dev/shm
 tmpfs                    16384         0     16384   0% /var/spool/MIMEDefang
 sunsite:/local/majordomo/lists
-                       6196236   4916832   1217440  81% 
/sunsite/majordomo/lists
+                       6196236   4916828   1217444  81% 
/sunsite/majordomo/lists
 sunsite:/recesja     123378104  42310704  81067400  35% /www2
change: -1.79692307692307692307 per second, ends: Fri Mar 27 21:02:44 MET 2009

We can use the 2nd run data instead of 1st run, note different time and
version 1.2:

address@hidden:/tmp,0# cmddiff -f 4.4 -e 0 -r 1.2 df
df
--- f1eddd11eb190a1271fde939bfc86883    2009/03/10 12:11:52     1.2
+++ f1eddd11eb190a1271fde939bfc86883    2009/03/10 12:17:51
@@ -1,12 +1,12 @@
 Filesystem           1K-blocks      Used Available Use% Mounted on
-/dev/sda1               489992    361000    103692  78% /
+/dev/sda1               489992    361001    103691  78% /
 /dev/mapper/sys-tmp    2031440     68908   1857676   4% /tmp
-/dev/mapper/sys-var    8125880   5016372   2690092  66% /var
+/dev/mapper/sys-var    8125880   5016976   2689488  66% /var
 /dev/mapper/sys-usr    5078656   1357396   3459116  29% /usr
-/dev/mapper/sys-home  11173104   8909572   1686908  85% /home
-/dev/mapper/sys-www   75164744  60372928  10912776  85% /www
+/dev/mapper/sys-home  11173104   8909556   1686924  85% /home
+/dev/mapper/sys-www   75164744  60377028  10908676  85% /www
 tmpfs                  1037824         0   1037824   0% /dev/shm
 tmpfs                    16384         0     16384   0% /var/spool/MIMEDefang
 sunsite:/local/majordomo/lists
-                       6196236   4916832   1217440  81% 
/sunsite/majordomo/lists
+                       6196236   4916828   1217444  81% 
/sunsite/majordomo/lists
 sunsite:/recesja     123378104  42310704  81067400  35% /www2
change: -1.68245125348189415041 per second, ends: Sun Mar 29 01:20:24 MET 2009

R.
-- 
Jeżeli upadnie cywilizacja zachodnia, to będzie szansa na odbudowę cywilizacji
      chrześcijańskiej. (dr Stanisław Krajski, Radio Maryja, 10 X 2001)