I have a string which comes from a variable I want to increment it. how can i do that using shell script?
this is my input which comes from a variable:
abc-ananya-01
output should be:
abc-ananya-02
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4 Answers
It is shorter:
a=abc-lhg-08
echo ${a%-*}-`printf "%02d" $((10#${a##*-}+1))`
abc-lhg-09
Even better:
a=abc-lhg-08
printf "%s-%02d\n" ${a%-*} $((10#${a##*-}+1))
abc-lhg-09
2 Comments
chepner
Nothing in this answer requires
bash 4, or even any bash extensions; it will work in any POSIX shell.
László Szilágyi
In my first example I found a fundamental problem and I corrected it. The original first example can't work with abc-lhg-08 or abc-lhg-09 inputs. I had to suppress the auto octal interpretation of bash when there was a leading zero, with explicit indication of radix ten 10#. I show you what I mean:
a=08;echo $(($a)) bash: 08: value too great for base (error token is "08") a=08;echo $((10#$a)) 8 And there is no reason to use both echo and printf so the second example more fits.Bash string manipulations can be used here.
a='abc-ananya-07'
let last=$(echo ${a##*-}+1)
echo ${a%-*}-$(printf "%02d" $last)
1 Comment
László Szilágyi
This solution doesn't work with these inputs: a='abc-ananya-08' or a='abc-ananya-09' bash error: bash: let: last=08: value too great for base (error token is "08") My correct answer is here: [stackoverflow.com/a/36934535/4581311]
check this:
kent$ echo "abc-ananya-07"|awk -F'-' -v OFS='-' '{$3=sprintf("%02d",++$3)}7'
abc-ananya-08
The above codes do the increment and keep your number format.
Comments
With pure Bash it is a bit long:
IFS="-" read -r -a arr <<< "abc-ananya-01"
last=10#${arr[${#arr}-1]} # to prevent getting 08, when Bash
# understands it is a number in base 8
last=$(( last + 1 ))
arr[${#arr}-1]=$(printf "%02d" $last)
( IFS="-"; echo "${arr[*]}" )
This reads into an array, increments the last element and prints it back.
It returns:
abc-ananya-02
4 Comments
chepner
bash 4.3 now allows negative subscripts, so you can write last=$((${arr[-1]}+1)) (it's short enough to make a one-liner reasonable).chepner
In fact, you can use
printf -v arr[-1] "%02d" $((arr[-1]+1)) to avoid the need for the temporary last variable altogether.László Szilágyi
This solution doesn't work with these inputs: a='abc-ananya-08' or a='abc-ananya-09' bash error: bash: let: last=08: value too great for base (error token is "08") My correct answer is here: [stackoverflow.com/a/36934535/4581311]
fedorqui
@LászlóSzilágyi yep, hadn't checked that one. Updated, thanks.