Delta -- a quick tool to see changing numeric values in the shell

Motivation

While debugging various issues you often get relevant data as always-increasing counters, like the Linux VM page fault stats:

$ for i in `seq 1 5` ; do grep fault /proc/vmstat ; sleep 1 ; done
pgfault 78258716080
pgmajfault 3202798
thp_fault_alloc 0
thp_fault_fallback 0
pgfault 78258733001
pgmajfault 3202799
thp_fault_alloc 0
thp_fault_fallback 0
pgfault 78258754872
pgmajfault 3202799
thp_fault_alloc 0
thp_fault_fallback 0
pgfault 78258833733
pgmajfault 3202799
thp_fault_alloc 0
thp_fault_fallback 0
pgfault 78258865018
pgmajfault 3202799
thp_fault_alloc 0
thp_fault_fallback 0

Now, quick: how many page faults per second were there? Did any major faults happen?

Let's say 20k-ish. Or let's see exactly:

$ timeout 5 delta grep fault /proc/vmstat
pgfault 78262968904
pgmajfault 3202834
thp_fault_alloc  0
thp_fault_fallback  0
--- Thu Nov 19 18:24:00 2015
pgfault      +33040
pgmajfault      +0
thp_fault_alloc +0
thp_fault_fallback +0
--- Thu Nov 19 18:24:01 2015
pgfault      +27092
pgmajfault      +0
thp_fault_alloc +0
thp_fault_fallback +0
--- Thu Nov 19 18:24:02 2015
pgfault       +7653
pgmajfault      +0
thp_fault_alloc +0
thp_fault_fallback +0
--- Thu Nov 19 18:24:03 2015
pgfault      +37106
pgmajfault      +0
thp_fault_alloc +0
thp_fault_fallback +0

delta works on all kinds of file formats with ints or floats (except scientific notation) and does its best to autodetect the number format for pretty output.

Demo

Installation

pip install git+https://github.com/gnosek/delta

Tested on Python 2.6, 2.7 and 3.5. Requires Click and ansicolors.