How do I split a string into two strings?

Question

I already know how to put h4 h7 h8 h9 h7 into an array with space as delimiter, but after that I am trying to separate the h from the numbers to compare the numbers to each other.

How can I do split these in a bash script?

Answer 1

#!/bin/bash

arr=( h4 h7 h8 h9 h7 )

for thing in "${arr[@]}"; do
    num=${thing#?}
    printf 'The number in "%s" is %d\n' "$thing" "$num"
done

The variable expansion ${variable#pattern} removes the shortest prefix string matching pattern from $variable. The pattern ? matches a single character.

The output will be

The number in "h4" is 4
The number in "h7" is 7
The number in "h8" is 8
The number in "h9" is 9
The number in "h7" is 7

Alternatively, to ignore remove the non-digit prefix regardless of how long it is, using sed,

#!/bin/bash

arr=( hello4 happy7 hobbit8 hulk9 hr-department7 )

for thing in "${arr[@]}"; do
    num=$( printf '%s\n' "$thing" | sed 's/^[^[:digit:]]*//' )
    printf 'The number in "%s" is %d\n' "$thing" "$num"
done

or, using regular expression matching of the digits at the end,

#!/bin/bash

arr=( hello4 happy7 hobbit8 hulk9 hr-department7 )

for thing in "${arr[@]}"; do
    if [[ "$thing" =~ ([[:digit:]]+)$ ]]; then
        printf 'The number in "%s" is %d\n' "$thing" "${BASH_REMATCH[1]}"
    fi
done