Using bash, how to assign integer to variable using echo

Question

I'd like to understand bash a bit better as I'm apparently horrible at it...

I'm trying to generate a sequence of constant width integers, but then test them to do something exceptional for particular values. Like so:

  for n in $(seq -w 1 150)
  do
    # The next line does not work: doit.sh: line 9: XX: command not found
    #decval= $( echo ${n} | sed 's/^0//g' | sed 's/^0//g' )
    #if [[ ${decal} -eq 98 ]] ; then
    if [[ $( echo ${n} | sed 's/^0//g' | sed 's/^0//g' ) -eq 98 ]] ; then
      echo "Do something different for 98"
    elif [[ $( echo ${n} | sed 's/^0//g' | sed 's/^0//g' ) -eq 105 ]] ; then
      echo "Do something different for 98"
    fi
  done

This script works for my purposes, but if I try and make the assignment 'decval= $(…' I get an error 'command not found'. I don't understand this, can someone explain?

Also, is there an improvement I can make to this script if I have a large number of exceptions to prevent a long list of if ; then elif … ?

It's probably easier to generate variable width, then convert to fixed width with a simple printf. For additional improvements, have a look at the shell's case statement. — tripleee
– tripleee, Commented Jan 18, 2014 at 18:00

John Kugelman · Accepted Answer · 2014-01-18 17:40:48Z

6

The problem is in the space between = and $:

decval= $(…

You should write without spaces:

decval=$(...

Because, if you write the space, your shell reads decval= as declval="" and treats the result of $(echo...) as the name of a command to execute, and obviously it doesn't find the command.

Also (just a small optimization), you can write:

sed 's/^0\+//'

instead of

sed 's/^0//g' | sed 's/^0//g'

Here:

0\+ means 0 one or more times;
g is removed, because g means replace all occurences in the string, and you have only one occurence (^ can be only one time in a string).

Also, you can check your variable even with leading zeros, without sed:

[[ "$n" =~  "0*98" ]]

edited Jan 18, 2014 at 17:40

John Kugelman

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answered Jan 18, 2014 at 10:17

Igor Chubin

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2 Comments

tripleee Over a year ago

Or even sed 's/^0*//' which should be portable to pretty much any platform.

highbandwidth Over a year ago

I could have sworn I'd tried that… so of course I didn't try it 'again'. D'Oh!

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