LinuxQuestions.org - Shell Script Arrays

- Programming (https://www.linuxquestions.org/questions/programming-9/)

- - Shell Script Arrays - Running cat (https://www.linuxquestions.org/questions/programming-9/shell-script-arrays-running-cat-505552/)

Shell Script Arrays - Running cat

I wanted to write a shell script that utilized a non-acpi-directory command line interface to the battery charge of my laptop (I won't bother to go into the reasons). Everything was doing just fine until I attempted to run a cat on the /proc/acpi/battery/BATx/state information and store it in an array.

The following code is what I am using for my "test"

Code:

# load the list of avaialble batteries

dirList=( $(ls -1 $BATT_DIR) )



# make sure we have data in the array

if [ ${#dirList[@]} -lt 1 ]; then

  echo "No batteries located (I looked in $BATT_DIR)!"

  exit 3

fi



# now, load the data for each battery

for element in $(seq 0 $((${#dirList[@]} - 1)))

do

  # data load

  batt=${dirList[$element]}

  battStats=( $(cat $BATT_DIR/$batt/state) )



  for battElement in $(seq 0 $((${#battStats[@]} - 1)))

  do

    echo ${battStats[$battElement]}

  done

done

The data actually winds up in the array, but not in the format I was expecting it to. I was expecting my use of cat to place each line of the cat into the array as an individual element, not each row and column.

The output this is giving me is this:

Code:

present:

yes

capacity

state:

ok

charging

state:

charging

present

rate:

unknown

remaining

capacity:

5760

mAh

present

voltage:

unknown

This output I am expecting is this:

Code:

present:                yes

capacity state:          ok

charging state:          charging

present rate:            unknown

remaining capacity:      5760 mAh

present voltage:        unknown

While the output I have is an acceptable "hack" for utilization in my script, it doesn't really provide what I had hoped. I wanted to parse the text in case the data in that file changes in future acpi/kernel releases instead of just relying on hard-coded indexes utilizing the colon character as my "end of label" indicator.

This concerns me because I also want to cat the /proc/acpi/battery/BATx/info file for the "design capacity" in order to calculate the percentage of battery life remaining. If either changes, my shell script will wind up vomiting all over me.

I wanted to avoid doing this in C/C++, even though it fits the solution as well. But I may wind up switching to that if I can't get this working.

Thanks.

i've not done this with arrays in bash directly, but i'm sure you need to look at the $IFS vairable. by default IFS (Input Field Seperateor) is white space, so to delimit the output you have, everything seperated by some form of white space is a different record. instead, you'd want to change $IFS to be a new line temporarily. try this:

IFS='\n' battStats=( $(cat $BATT_DIR/$batt/state) )

Doing that is actually giving me a syntax error:

Code:

line 60: 0

1

2

3

4

5

6

7

8

9

10

11: syntax error in expression (error token is "1

2

3

4

5

6

7

8

9

10

11")

I attempted utilizing what you posted in two separate code format styles just to be safe as well. First I did exactly what you posted, second I separated the IFS and battStat population to two separate lines.

BTW... line 60 is the echo statement in this snippet:

Code:

for battElement in $(seq 0 $((${#battStats[@]} - 1)))

  do

    echo ${battStats[$battElement]}

  done

In another thread I've found that there should be

Code:

IFS=$'\n'

which works perfectly for me. Anyone know why there must be the $ sign? It doesn't work withou it.

HUZZAH!!
Thank you SO much!

That works perfectly.
Now to just finish up the rest of my script.