split svnversion output in bash

Question

I have this function, works fine, but I would like to rewrite it in bash. the problem is, I have too little knowledge of what's available in bash.

#!/usr/bin/python

def parse_svnversion(value):
    """split the output of svnversion into its three components

    given a string that looks like the output of the command
    svnversion, returns the 3-tuple (low, high, flags)

    >>> parse_svnversion('1024')
    (1024, 1024, '')
    >>> parse_svnversion('1024:2000')
    (1024, 2000, '')
    >>> parse_svnversion('1024M')
    (1024, 1024, 'M')
    >>> parse_svnversion('1024:2000MP')
    (1024, 2000, 'MP')
    """

    values = filter(lambda x: x.isdigit() or x==':', value).split(':')
    return int(values[0]), int(values[-1]), filter(str.isalpha, value)

if __name__ == '__main__':
    import doctest
    doctest.testmod()

what I would like is a similarly small bash function that I can invoke and that will set something (three variables? an array?) that I can use. if it's an array, I would really like it to be of fixed size (3).

Answer 1

you can use this subroutine

parsesvn(){
 toparse="$1"
 num=${toparse%%[A-Z]*}
 alpha=${toparse##*[0-9]}
 IFS=":"
 set -- $num
 for i in $@
 do
    printf "%s " $i
 done
 if [ ! -z "$alpha" ];then
    printf "%s" "$alpha"
 fi
}

# main #
var=$(parsesvn "1024:2000")
set -- $var
if [ "$1" -lt "$2" ];then
    echo "ok"
    greater=$2
else
    echo "LHS: $1 greater than RHS: $2"
fi
echo "greater is $greater"

Answer 2

The following solution stores the values into the array arr[ ] to match your original tuple as closely as possible. After the if-else-fi block you can do whatever you want with arr[0],arr[1], and arr[2]. I tried to match your post (and comment) as closely as possible. Also, I took the liberty to send the warning and notice messages to STDERR rather than STDOUT thinking you probably want to separate those.

#!/bin/bash

parse_svnversion()
{
    if [[ "$1" = *:* ]]; then
        arr[0]=${1%:*}
        arr[2]=${1//[0-9:]/}
        tmp_arr[1]=${1#*:}
        arr[1]=${tmp_arr[1]//${arr[2]}/}
    else
        arr[2]=${1//[0-9:]/}
        arr[0]=${1//${arr[2]}/}
        arr[1]=${arr[0]}
    fi

    echo ${arr[@]} 

    head_rev=$( (( ${arr[0]} > ${arr[1]} )) && echo ${arr[0]} || echo ${arr[1]} )
    echo "Notice: head revision is $head_rev" >&2

    if (( ${arr[1]} < ${arr[0]} )); then
        echo "Warning: you're working with mixed revisions" >&2
    fi
    if [[ -n ${arr[2]} ]]; then
        echo "Warning: there are flags" >&2
    fi
}

parse_svnversion "1024"
parse_svnversion "1024:2000"
parse_svnversion "1024M"
parse_svnversion "1024:2000MP"
parse_svnversion "2000:1024M"

Result without STDERR (sent to /dev/null)

$ ./svn_split.sh 2> /dev/null
1024 1024
1024 2000
1024 1024 M
1024 2000 MP
2000 1024 M

Result with STDERR

$ ./svn_split.sh
1024 1024
Notice: head revision is 1024
1024 2000
Notice: head revision is 2000
1024 1024 M
Notice: head revision is 1024
Warning: there are flags
1024 2000 MP
Notice: head revision is 2000
Warning: there are flags
2000 1024 M
Notice: head revision is 2000
Warning: you're working with mixed revisions
Warning: there are flags

Answer 3

This creates an array called "tuple" with three elements:

[[ $(svnversion .) =~ ([0-9]+):*([0-9]*)([A-Z]*) ]]
tuple[0]=${BASH_REMATCH[1]}
tuple[1]=${BASH_REMATCH[2]:-${tuple[0]}}
tuple[2]=${BASH_REMATCH[3]:-''}

Requires Bash 3.2 or greater. It may work in Bash >= 3 and < 3.2. Not portable to the Bourne shell, although it can be adapted for the Korn shell or the Z shell.

ksh uses the .sh.match array variable, for example: ${.sh.match[1]}

zsh uses the match array variable, for example: ${match[1]} or you can do

setopt bashrematch ksharrays

to have it work with the Bash version exactly as above.

The brace substitutions should be the same for all three.