periodic "value too great for base" doing math on date output in bash

Question

    ubu@bruntu:/home/wideDB1$ echo $(($(date +%s%N)/1000000))
1441637184683
ubu@bruntu:/home/wideDB1$ echo $(($(date +%N)/1000000))
730
ubu@bruntu:/home/wideDB1$ echo $(($(date +%N)/1000))
bash: 088253206: value too great for base (error token is "088253206")
ubu@bruntu:/home/wideDB1$ echo $(($(date +%N)/1000))
bash: 085061725: value too great for base (error token is "085061725")
ubu@bruntu:/home/wideDB1$ echo $(($(date +%N)/10000))
59078
ubu@bruntu:/home/wideDB1$ echo $(($(date +%N)/1000))
672523
ubu@bruntu:/home/wideDB1$ echo $(($(date +%N)/10))
12079796
ubu@bruntu:/home/wideDB1$ echo $(($(date +%N)/10000))
74644
ubu@bruntu:/home/wideDB1$ echo $(($(date +%N)/100000))
1403
ubu@bruntu:/home/wideDB1$ echo $(($(date +%N)/1000000))
5
ubu@bruntu:/home/wideDB1$ echo $(($(date +%N)/100000))
9977
ubu@bruntu:/home/wideDB1$ echo $(($(date +%N)/1000000))
360
ubu@bruntu:/home/wideDB1$ echo $(($(date +%N)/100000))
6663
ubu@bruntu:/home/wideDB1$ echo $(($(date +%N)/10))
10325856
ubu@bruntu:/home/wideDB1$ echo $(($(date +%N)/100))
8020128
ubu@bruntu:/home/wideDB1$ echo $(($(date +%N)/1000))
9461
ubu@bruntu:/home/wideDB1$ echo $(($(date +%N)/10000))
81272
ubu@bruntu:/home/wideDB1$ echo $(($(date +%N)/10000))
bash: 046340492: value too great for base (error token is "046340492")

I must use this function in a bash script accurately for synchronizing milliseconds between tasks but here is very unstable. Anyone can help me to figure out what best solution for this work?

Cheers! Alessandro

You get 'value too great' errors because the leading zero indicates an octal number for the shell when doing arithmetic. You can remove it by sed -E 's/^0//'. — user1666959, Sep 07 '15 at 15:46
@user1666959, boo hiss re: suggesting calling an external tool for something the shell can do built-in. — Charles Duffy, Sep 07 '15 at 22:33

score 2 · Answer 1 · answered Sep 07 '15 at 22:24

2

A string of digits beginning with 0 is treated as an octal number by default; you just need to tell bash to treat the string captured from date +%N as a decimal number in all cases, by prefix it with 10#.

$ echo $(( 10#$(date +%N)/1000000))

answered Sep 07 '15 at 22:24

chepner

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Thank you a lot it seems working good! Cheers! – Alessandro Sep 08 '15 at 08:20

score 1 · Answer 2 · answered Sep 07 '15 at 16:03

Digit strings inside of $((...)) are interpreted as numbers, but numbers starting with 0 are interpreted as octal numbers, i.e. in base 8.

You can easily remove the leading zeroes by parameter expansion:

#!/bin/bash
shopt -s extglob          # Enable extended globbing -- in this case, +(0)

for i in {1..20} ; do
    nanos=$(date +%N)
    echo -n "$nanos -> "
    nanos=${nanos##+(0)}  # Remove as many 0's from the left as possible.
    echo $nanos
done

periodic "value too great for base" doing math on date output in bash

2 Answers2