a question regarding proper printf(3) formating and alignment

[Karl Vogel]

>> In the last episode (Nov 17), Alexander Best said:

A> i've looked at a lot of utilities in the bsd src tree and most of them
A> seem to be doing something like this:

A> Device          1M-blocks     Used    Avail Capacity
A> /dev/label/swapfs     10239        0    10239     0%
A> /dev/label/swap      8191        0     8191     0%
A> Total               18431        0    18431     0%

A> i'd like to learn of ways formatting the header so that it aligns
A> properly, whether the device name is 10 chars long or 1000.

   ports/textproc/align is a nifty perl script that'll do this for just
   about any type of column-based input.  If you just want to fix "df" and
   you know how long the longest device name is, try something like this:

     #!/bin/ksh
     #<df: human-readable aligned output from df
     PATH=/bin:/usr/bin
     BLOCKSIZE=1m
     export PATH BLOCKSIZE

     scr='
       s/Available/Avail/
       s/Capacity/Cap/
       s/Mounted/Mount/
     '

     exec df ${1+"$@"} |
         sed -e "$scr" |
         awk '{printf "%-18s %12s %8s %8s %4s  %s\n", $1,$2,$3,$4,$5,$6}'
     exit 1

   Comparison:

     me% /bin/df /rd* /stage
     Filesystem  1M-blocks   Used  Avail Capacity  Mounted on
     /dev/ad0s1f    224821  55691 151144    27%    /rd01
     /dev/ad1s1g    226611  34497 173985    17%    /rd02
     /dev/ad3s1a    263974 198167  44688    82%    /rd03
     /dev/ad3s1g      3962    174   3471     5%    /stage

     me% ./df /rd* /stage
     Filesystem            1M-blocks     Used    Avail  Cap  Mount
     /dev/ad0s1f              224821    55691   151144  27%  /rd01
     /dev/ad1s1g              226611    34497   173985  17%  /rd02
     /dev/ad3s1a              263974   198167    44688  82%  /rd03
     /dev/ad3s1g                3962      174     3471   5%  /stage

>> On Wed, 17 Nov 2010 13:55:21 -0600, 
>> Dan Nelson <dnelson at allantgroup.com> happily babbled in reply:

D> I seem to remember /usr/bin/find doing this dynamically by expanding
D> columns as it saw values that were larger than the previous max, but
D> apparently not (I just tested it).

   I believe you're thinking of "file".

-- 
Karl Vogel                      I don't speak for the USAF or my company

When a man says it's a silly, childish game,
it's probably something his wife can beat him at.         --Epperson's law