Bash index of first character not given

Question

So basically something like expr index '0123 some string' '012345789' but reversed.
I want to find the index of the first character that is not one of the given characters...
I'd rather not use RegEx, if it is possible...

Why would you rather not use regex? – Andreas Louv Mar 22 '16 at 21:08 — Andreas Louv, Mar 22 '16 at 21:08
@andlrc I find it difficult to read... – Emma Mar 22 '16 at 21:32 — Emma, Mar 22 '16 at 21:32

score 1 · Accepted Answer · answered Mar 22 '16 at 21:14

1

You can remove chars with tr and pick the first from what is left

left=$(tr -d "012345789" <<< "0123_some string"); echo ${left:0:1}
_

once you have the char to find the index follow the same

expr index "0123_some string" ${left:0:1}
5

answered Mar 22 '16 at 21:14

karakfa

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score 1 · Answer 2 · answered Mar 22 '16 at 21:23

Using gnu awk and FPAT you can do this:

str="0123 some string"

awk -v FPAT='[012345789]+' '{print length($1)}' <<< "$str"
4

awk -v FPAT='[02345789]+' '{print length($1)}' <<< "$str"
1

awk -v FPAT='[01345789]+' '{print length($1)}' <<< "$str"
2

awk -v FPAT='[0123 ]+' '{print length($1)}' <<< "$str"
5

Andreas Louv · Answer 3 · 2016-03-22T21:21:17.610

0

I know this is in Perl but I got to say that I like it:

$ perl -pe '$i++while s/^\d//;$_=$i' <<< '0123 some string'
4

In case of 1-based index you can use $. which is initialized at 1 when dealing with single lines:

$ perl -pe '$.++while s/^\d//;$_=$.' <<< '0123 some string'
5

I'm using \d because I assume that you by mistake left out the number 6 from the list 012345789

Index is currently pointing to the space:

0123 some string
    ^ this space

edited Mar 22 '16 at 21:21

answered Mar 22 '16 at 21:12

Andreas Louv

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I think index is `1` based. – karakfa Mar 22 '16 at 21:19
@karakfa True might be :-) – Andreas Louv Mar 22 '16 at 21:21

score 0 · Answer 4 · answered Mar 22 '16 at 21:43

Even if shell globing might look similar, it is not a regex.

It could be done in two steps: cut the string, count characters (length).

#!/bin/dash
a="$1"                  ### string to process
b='0-9'                 ### range of characters not desired.
c=${a%%[!$b]*}          ### cut the string at the first (not) "$b".
echo "${#c}"            ### Print the value of the position index (from 0).

It is written to work on many shells (including bash, of course).

Use as:

$ script.sh "0123_some string"
4
$ script.sh "012s3_some string"
3

Bash index of first character not given

4 Answers4