CODEWITHSUNDEEP
bashshellautomation
umer
umer

Reputation: 27

need help in formatted output using for loop in shell script

I have the requirement to capture pod memory and other details in my setup. have written small reproducible shell script as copied below.

LOGFILE='/root/User1/test/log'
Data=""
space="   "
e=34
f=12Mi
a=122
b=123
c=333
d=450

for i in {1..10}; do
    Data+=$space
    Data+=$a
    Data+=$space
    Data+=$b
    Data+=$space
    Data+=$c
    Data+=$space
    Data+=$d
    Data+=$space
    Data+=$e 
    Data+=$space
    Data+=$f
    printf "%s" "$Data" >> ${LOGFILE}
    echo $'\n' >> ${LOGFILE}
    $(unset ${Data})
    
done

The above script produces concatenated output.

34   12Mi   122   123   333   450

34   12Mi   122   123   333   450   34   12Mi   122   123   333   450

34   12Mi   122   123   333   450   34   12Mi   122   123   333   450   34   12Mi   122   123   333   450

34   12Mi   122   123   333   450   34   12Mi   122   123   333   450   34   12Mi   122   123   333   450   34   12Mi   122   123   333   450

34   12Mi   122   123   333   450   34   12Mi   122   123   333   450   34   12Mi   122   123   333   450   34   12Mi   122   123   333   450   34   12Mi   122   123   333   450

34   12Mi   122   123   333   450   34   12Mi   122   123   333   450   34   12Mi   122   123   333   450   34   12Mi   122   123   333   450   34   12Mi   122   123   333   450   34   12Mi   122

The output format what I am looking for is

34   12Mi   122   123   333   450

34   12Mi   122   123   333   450
 
34   12Mi   122   123   333   450

34   12Mi   122   123   333   450

34   12Mi   122   123   333   450

34   12Mi   122   123   333   450

34   12Mi   122   123   333   450

34   12Mi   122   123   333   450

can some one help me here to understand what mistake I am doing here. and what could be the possible solution for this.

Upvotes: 0

Views: 48

Answers (1)

Benjamin W.
Benjamin W.

Reputation: 52316

When you do $(unset ${Data}), you are running unset ${Data} in a subshell, and then try to run its output (the empty string) as a command. This is wrong on a few levels:

  • A subshell can't affect its parent environment, and you don't want to run the output as a command anyway
  • unset takes the name of the variable, not its expansion, as a parameter

The quick fix is to replace $(unset ${Data}) with unset Data.

A simpler overall approach could be to skip the intermediate variable entirely, and move the redirection out of the loop:

for i in {1..10}; do
    printf '%s   ' "$e" "$f" "$a" "$b" "$c"
    printf '%s\n\n' "$d"
done >> "$LOGFILE"

This doesn't require $Data or $space any longer.

This prints the exact desired output you show, though the actual output you show doesn't correspond to your script, which has each line begin with three blanks. To get that, the printf formatting strings would have to be ' %s' and ' %s\n\n', respectively.

Upvotes: 2

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