ecalc 0.2

a simple Python-based calculator for network engineers/researchers

NAME

ecasl - a simple Python-based calculator for network engineers/researchers.

SYNOPSIS

ecalc [-d] [-p #]

DESCRIPTION

This manual page documents ecalc. This program is an interactive text-based calculator written in Python supporting GNU readline library. ecalc is specifically designed for network engineers/researchers since it can easily handle network-related units such as bit, byte, packet, bps, and bit/s.

After invocation, ecalc displays a prompt "?", and ask for a user to enter an arbitrary expression to be calculated, which must be a valid Python expression. ecalc then evaluates the expression as-is, and displays the return value in a decimal format, followed by values in hexadecimal, octal, and binary formats.

For typical daily use, the following mathematical functions and constants imported from the Python standard math module would be convenient. See https://docs.python.org/3/library/math.html for the detail of other mathematical functions.

• functions

  ceil, comb, copysign, fabs, factorial, floor, fmod, frexp, fsum, gcd, isclose, isfinite, isinf, isnan, isqrt, lcm, ldexp, modf, nextafter, perm, prod, remainder, trunc, ulp, exp, expml, log, loglp, log2, log10, pow, sqrt, asin, atan, atan2, cos, dist, hypot, sin, tan, degrees, radians, acosh, asinh, atanh, cosh, sinh, tanh, erf, erfc, gamma, lgamma,

• constants

  pi, e, tau, inf, nan

Note that ecalc supports GNU readline library, so that a user can interactively edit his/her input with Emacs-like (user-configurable) key bindings. See the manual page of GNU readline library for the details.

ecalc understands the following units, which must be enclosed in square brackets.

s            second
m            meter
bit          bit
bps          bit per second
byte, B      byte
pkt, packet  packet

By default, packet size is assumed to be 1,500 [byte] (i.e., the maximum Ethernet payload size), but it can be changed by -p option.

ecalc supports the following prefixes.

p     pico   10**-12
n     nano   10**-9
u     micro  10**-6
m     milli  10**-3
k, K  kilo   10**3
M     mega   10**6
G     giga   10**9
T     tera   10**12
P     peta   10**15

In ecalc, the base unit is either second or byte, and all values in other than second or byte are automatically converted. For example, 1,000 [bit/ms] is automatically converted to 125,000 [byte/s]. See EXAMPLES for detailed usage of ecalc.

EXAMPLES

This section shows an example session with ecalc.

A simple arithmetic calculation:

? 1+2*(3+4/5)**6
%1 = 6022.872767999998
        1786 hex          13606 oct   00000000 00000000 00010111 10000110
       48.18 bit/ms   4.818e+04 bit/s        48.18 Kbit/s     0.04818 Mbit/s
       6.023 B/ms          6023 B/s          6.023 KB/s      0.006023 MB/s  
    0.004015 pkt/ms       4.015 pkt/s    1.807e+12 m        1.807e+09 km    

Blank spaces are arbitrary.

? 1 + 2 * (3 + 4 / 5) ** 6
%2 = 6022.872767999998
        1786 hex          13606 oct   00000000 00000000 00010111 10000110
       48.18 bit/ms   4.818e+04 bit/s        48.18 Kbit/s     0.04818 Mbit/s
       6.023 B/ms          6023 B/s          6.023 KB/s      0.006023 MB/s  
    0.004015 pkt/ms       4.015 pkt/s    1.807e+12 m        1.807e+09 km    

The previous result can be referred by "%".

? % + 1
%3 = 6023.872767999998
        1787 hex          13607 oct   00000000 00000000 00010111 10000111
       48.19 bit/ms   4.819e+04 bit/s        48.19 Kbit/s     0.04819 Mbit/s
       6.024 B/ms          6024 B/s          6.024 KB/s      0.006024 MB/s  
    0.004016 pkt/ms       4.016 pkt/s    1.807e+12 m        1.807e+09 km    

Past results can be referred by "%N".

? %1 - %2
%4 = 0.0
           0 hex              0 oct   00000000 00000000 00000000 00000000
           0 bit/ms           0 bit/s            0 Kbit/s           0 Mbit/s
           0 B/ms             0 B/s              0 KB/s             0 MB/s  
           0 pkt/ms           0 pkt/s            0 m                0 km    

Python builtin functions can be used.

? int(%1)
%5 = 6022
        1786 hex          13606 oct   00000000 00000000 00010111 10000110
       48.18 bit/ms   4.818e+04 bit/s        48.18 Kbit/s     0.04818 Mbit/s
       6.022 B/ms          6022 B/s          6.022 KB/s      0.006022 MB/s  
    0.004015 pkt/ms       4.015 pkt/s    1.807e+12 m        1.807e+09 km    
  ? log(sin(1) + cos(2))
%6 = -0.8549036989769139
           0 hex              0 oct   00000000 00000000 00000000 00000000
   -0.006839 bit/ms      -6.839 bit/s    -0.006839 Kbit/s  -6.839e-06 Mbit/s
  -0.0008549 B/ms       -0.8549 B/s     -0.0008549 KB/s    -8.549e-07 MB/s  
  -5.699e-07 pkt/ms  -0.0005699 pkt/s   -2.565e+08 m       -2.565e+05 km    

Binary, octal, and hexadecimal numbers as well as decimal numbers can be combined.

? 1234 + 0b101100111 + 0o1234 + 0x1234
%7 = 6921
        1b09 hex          15411 oct   00000000 00000000 00011011 00001001
       55.37 bit/ms   5.537e+04 bit/s        55.37 Kbit/s     0.05537 Mbit/s
       6.921 B/ms          6921 B/s          6.921 KB/s      0.006921 MB/s  
    0.004614 pkt/ms       4.614 pkt/s    2.076e+12 m        2.076e+09 km    

Example usage of some builtin functions:

? sqrt(2943)
%8 = 54.249423960075376
          36 hex             66 oct   00000000 00000000 00000000 00110110
       0.434 bit/ms         434 bit/s        0.434 Kbit/s    0.000434 Mbit/s
     0.05425 B/ms         54.25 B/s        0.05425 KB/s     5.425e-05 MB/s  
   3.617e-05 pkt/ms     0.03617 pkt/s    1.627e+10 m        1.627e+07 km    
  ? abs(%)
%9 = 54.249423960075376
          36 hex             66 oct   00000000 00000000 00000000 00110110
       0.434 bit/ms         434 bit/s        0.434 Kbit/s    0.000434 Mbit/s
     0.05425 B/ms         54.25 B/s        0.05425 KB/s     5.425e-05 MB/s  
   3.617e-05 pkt/ms     0.03617 pkt/s    1.627e+10 m        1.627e+07 km    
? abs(-%)
%10 = 54.249423960075376
          36 hex             66 oct   00000000 00000000 00000000 00110110
       0.434 bit/ms         434 bit/s        0.434 Kbit/s    0.000434 Mbit/s
     0.05425 B/ms         54.25 B/s        0.05425 KB/s     5.425e-05 MB/s  
   3.617e-05 pkt/ms     0.03617 pkt/s    1.627e+10 m        1.627e+07 km    

Convert a transmission rate in several units:

? 123 [packet/ms]
%11 = 184500000.0
     aff3f20 hex     1277637440 oct   00001010 11111111 00111111 00100000
   1.476e+06 bit/ms   1.476e+09 bit/s    1.476e+06 Kbit/s        1476 Mbit/s
   1.845e+05 B/ms     1.845e+08 B/s      1.845e+05 KB/s         184.5 MB/s  
         123 pkt/ms    1.23e+05 pkt/s    5.535e+16 m        5.535e+13 km    

From the above result, one can see that 123 [packet/ms] is equivalent to 1,476 [Mbit/s] with 1,500 [byte] packet.

Product of transmission rate and duration gives the total amount of data transferred.

? % * 10 [s]
%12 = 1845000000.0
    6df87740 hex    15576073500 oct   01101101 11111000 01110111 01000000
   1.476e+07 bit/ms   1.476e+10 bit/s    1.476e+07 Kbit/s   1.476e+04 Mbit/s
   1.845e+06 B/ms     1.845e+09 B/s      1.845e+06 KB/s          1845 MB/s  
        1230 pkt/ms    1.23e+06 pkt/s    5.535e+17 m        5.535e+14 km    

Thus, if you continuosly send for 10 [s] at the transmission rate of 123 [packet/ms], the total volume transferred is 1,845 [MB].

Data size divided by duration gives the transmission rate.

? 6.4[Gbyte]/120[s]
%13 = 53333333.333333336
     32dcd55 hex      313346525 oct   00000011 00101101 11001101 01010101
   4.267e+05 bit/ms   4.267e+08 bit/s    4.267e+05 Kbit/s       426.7 Mbit/s
   5.333e+04 B/ms     5.333e+07 B/s      5.333e+04 KB/s         53.33 MB/s  
       35.56 pkt/ms   3.556e+04 pkt/s      1.6e+16 m          1.6e+13 km    

So, if 6.4 [Gbyte] is trensferred in 120 [s], the transmission rate of the network is 426.7 [Mbit/s].

Calculating the bandwidth-delay product:

? 64[packet] * 1200[ms]
%14 = 115200.0
       1c200 hex         341000 oct   00000000 00000001 11000010 00000000
       921.6 bit/ms   9.216e+05 bit/s        921.6 Kbit/s      0.9216 Mbit/s
       115.2 B/ms     1.152e+05 B/s          115.2 KB/s        0.1152 MB/s  
      0.0768 pkt/ms        76.8 pkt/s    3.456e+13 m        3.456e+10 km    

which indicates that, for instance, the TCP socket buffer of 11.52 [KB] is at least required for TCP window flow control with its window size of 64 [packet] and the round-trip time of 120 [ms].

Values in meters are converted to seconds --- time to need to travel in the speed of the light.

? 128[km]
%15 = 0.00042666666666666667
           0 hex              0 oct   00000000 00000000 00000000 00000000
   3.413e-06 bit/ms    0.003413 bit/s    3.413e-06 Kbit/s   3.413e-09 Mbit/s
   4.267e-07 B/ms     0.0004267 B/s      4.267e-07 KB/s     4.267e-10 MB/s  
   2.844e-10 pkt/ms   2.844e-07 pkt/s     1.28e+05 m              128 km    

which shows the light travels 128 [km] in 0.000426 [s].

Conversely, values in seconds are displayed in meters.

? 0.0012[ms]
%16 = 1.2e-06
           0 hex              0 oct   00000000 00000000 00000000 00000000
     9.6e-09 bit/ms     9.6e-06 bit/s      9.6e-09 Kbit/s     9.6e-12 Mbit/s
     1.2e-09 B/ms       1.2e-06 B/s        1.2e-09 KB/s       1.2e-12 MB/s  
       8e-13 pkt/ms       8e-10 pkt/s          360 m             0.36 km    

So, one can see that the light travels 0.36 [km] in 0.0012 [ms].

AVAILABILITY

The latest version of ecalc is available at

AUTHOR

Hiroyuki Ohsaki <ohsaki[atmark]lsnl.jp>