42 Improving the Readability of df Output
#42 Improving the Readability of df Output
While Script #41 summarized df command output, the most important change we can make to df is simply to improve the readability of its output.
The Code
#!/bin/sh # newdf - A friendlier version of df. awkscript="/tmp/newdf.$$" trap "rm -f $awkscript" EXIT cat << 'EOF' > $awkscript function showunit(size) { mb = size / 1024; prettymb=(int(mb * 100)) / 100; gb = mb / 1024; prettygb=(int(gb * 100)) / 100; if (substr(size,1,1) !~ "[0-9]" substr(size,2,1) !~ "[0-9]") { return size } else if (mb < 1) { return size "K" } else if (gb < 1) { return prettymb "M" } else { return prettygb "G" } } BEGIN { printf "%-27s %7s %7s %7s %8s %-s\n", "Filesystem", "Size", "Used", "Avail", "Capacity", "Mounted" } !/Filesystem/ { size=showunit(); used=showunit(); avail=showunit(); printf "%-27s %7s %7s %7s %8s %-s\n", , size, used, avail, , } EOF df -k awk -f $awkscript exit 0 How It Works
Much of the work in this script takes place within an awk script, and it wouldn't be too much of a step to write the entire script in awk rather than in the shell, using the system() function to call df directly. This script would be an ideal candidate to rewrite in Perl, but that's outside the scope of this book.
There's also a trick in this script that comes from my early days of programming in BASIC, of all things:
prettymb=(int(mb * 100)) / 100;
When working with arbitrary-precision numeric values, a quick way to limit the number of fractional digits is to multiply the value by a power of 10, convert it to an integer (which drops the fractional portion), and then divide it back by the same power of 10. In this case, a value like 7.085344324 is turned into the much more attractive 7.08.
| Note | Some versions of df have an -h flag that offers an output format similar to this script's output format. However, as with many of the scripts in this book, this one will let you achieve friendly and more meaningful output on every Unix or Linux system, regardless of what version of df is present. |
Running the Script
This script has no arguments and can be run by anyone , root or otherwise . To eliminate reporting space usage on devices that you aren't interested in, use grep -v after the call to df .
The Results
Regular df reports are difficult to understand:
$ df Filesystem 512-blocks Used Avail Capacity Mounted on /dev/disk1s9 78157200 43187712 34457488 55% / devfs 196 196 0 100% /dev fdesc 2 2 0 100% /dev <volfs> 1024 1024 0 100% /.vol /dev/disk0s9 234419552 71863152 162556416 30% /Volumes/110GB
The new script exploits awk to improve readability:
$ newdf Filesystem Size Used Avail Capacity Mounted /dev/disk1s9 37.26G 20.59G 16.43G 55% / devfs 98K 98K 0 100% /dev fdesc 1 1 0 100% /dev <volfs> 512K 512K 0 100% /.vol /dev/disk0s9 111.77G 34.26G 77.51G 30% /Volumes/110GB
