Trouble adding an integer to an array element in shell script

Question

I am trying to parse the output on svn info without resorting to an external shell command like sed or awk. This is purely academic as I know I could do this in a heartbeat with those tools.

Output I am parsing is:

Path: .
URL: svn://[email protected]/handbrake_batch/trunk/handbrake
Repository Root: svn://[email protected]/handbrake_batch
Repository UUID: 99c2cca7-102b-e211-ab20-02060a000c0b
Revision: 6
Node Kind: directory
Schedule: normal
Last Changed Author: ilium007
Last Changed Rev: 6
Last Changed Date: 2012-11-10 19:00:35 +1000 (Sat, 10 Nov 2012)

Here is my code:

#!/bin/bash

#set -x

OLD_IFS="$IFS"
IFS=$'\r\n'

# Get the output from svn info into an array
SVN_INFO_ARR=(`svn info`)
COUNT=0
for i in ${SVN_INFO_ARR[@]}; do
    echo $COUNT
    echo "$i"
    (( COUNT++ ))
done

# Get the element that says "Revision: 6"
REV_ARR=${SVN_INFO_ARR[4]}

# Testing the loop over what should be a two element array
COUNT=0
for i in ${REV_ARR[@]}; do
    echo $COUNT
    echo "$i"
    (( COUNT++ ))
done

#This should give the number 6 (or string or something)
REV_NUMBER=${REV_ARR[1]}

echo ${REV_NUMBER}

### INCREMENT REVISION NUMBER FROM ARRAY ELEMENT ###

#NEW_REV_NUMBER= ????? + 1

IFS="$OLD_IFS"

I would like to be able to take the string:

Revision: 6

and pull out the 6 and increment by 1 so I can update a release txt file to be included in the SVN commit.

I have tried to make that 6 turn into a 7 for an hour now and feel like an idiot because I can't do it.

F. Hauri - Give Up GitHub · Accepted Answer · 2012-11-10 22:20:48Z

3

You need parenthesis: Change this:

# Get the element that says "Revision: 6"
REV_ARR=${SVN_INFO_ARR[4]}

to this:

# Get the element that says "Revision: 6"
REV_ARR=(${SVN_INFO_ARR[4]})

before

#This should give the number 6 (or string or something)
REV_NUMBER=${REV_ARR[1]}

so you'll be able to:

((REV_NUMBER++))

Edit:

As you wrote:

SVN_INFO_ARR=(`svn info`)

instead of just:

SVN_INFO_ARR=`svn info`

The parenthesis is used in bash to define an array. Have a look at:

man -Len -P'less +"/^ *Arrays"' bash

edited Nov 10, 2012 at 22:20

answered Nov 10, 2012 at 14:05

F. Hauri - Give Up GitHub

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3 Comments

ilium007 Over a year ago

It was the parentheses that I was looking for - thanks @f-hauri Can you please explain the parentheses ?

ilium007 Over a year ago

Actually it doesn't work !! Can you please explain the parentheses ? New code:

#!/bin/bash  set -x  OLD_IFS="$IFS" IFS=$'\r\n'  # Get the output from svn info into an array SVN_INFO_ARR=(`svn info`)  IFS="$OLD_IFS"  # Get the element that says "Revision: 6" REV_ARR=(${SVN_INFO_ARR[4]})  #This should give the number 6 (or string or something) REV_NUMBER=${REV_ARR[1]} echo $REV_NUMBER echo ((REV_NUMBER++))

Output error:

+ REV_ARR=(${SVN_INFO_ARR[4]}) + REV_NUMBER=6 + echo 6 6 ./test.sh: line 19: syntax error near unexpected token `(' ./test.sh: line 19: `echo ((REV_NUMBER++))'

ilium007 Over a year ago

Accepted answer after being advised further down the ++ syntax.

doubleDown · Accepted Answer · 2012-11-10 14:41:23Z

3

Instead of hardcoding the array indices, a better way would be to filter out the line you need and extract the number

Here's one way using regex (Bash 4)

while read -r line; do
    if [[ $line =~ Revision:\ ([0-9]+) ]]; then
         new_rev_num=$((BASH_REMATCH[1]+1))
         echo $new_rev_num
         break
    fi
done < $(svn info)

answered Nov 10, 2012 at 14:41

doubleDown

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Comments

choroba · Accepted Answer · 2012-11-10 13:48:16Z

0

Use grep to only select the line you need. Then, use Parameter expansion to remove "Revision: ". Finally, use let to do the arithmetics:

REVISION=$(svn info | grep '^Revision:')
REVISION=${REVISION#* }
let REVISION++

answered Nov 10, 2012 at 13:48

choroba

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1 Comment

ilium007 Over a year ago

Thanks @choroba but I wanted to tackle this without calling an external tool such as grep but your syntax is useful and I will keep in mind for other projects.

ilium007 · Accepted Answer · 2012-11-10 22:24:43Z

0

This code worked in the end:

#!/bin/bash

set -x

OLD_IFS="$IFS"
IFS=$'\r\n'

# Get the output from svn info into an array
SVN_INFO_ARR=(`svn info`)

IFS="$OLD_IFS"

# Get the element that says "Revision: 6"
REV_ARR=(${SVN_INFO_ARR[4]})

#This should give the number 6 (or string or something)
REV_NUMBER=${REV_ARR[1]}
echo $REV_NUMBER
echo $(( REV_NUMBER + 1 ))

The answer above had me stumped for a while because it was missing the $ in front of:

echo $(( REV_NUMBER + 1 ))

and the ((REV_NUMBER++)) notation did not work, I still got 6, not 7:

+ OLD_IFS='     
'
+ IFS='
'
+ SVN_INFO_ARR=(`svn info`)
++ svn info
+ IFS='     
'
+ REV_ARR=(${SVN_INFO_ARR[4]})
+ REV_NUMBER=6
+ echo 6
6
+ echo 6
6

answered Nov 10, 2012 at 22:24

ilium007

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2 Comments

doubleDown Over a year ago

((REV_NUMBER++)) only increments REV_NUMBER after you echo it, ((++REV_NUMBER)) would give you the right number.

ilium007 Over a year ago

Ok - that now makes 100% sense. Thanks.

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