How to fetch values from a line in a file to variables in UNIX?

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Top Forums Shell Programming and Scripting How to fetch values from a line in a file to variables in UNIX?
# 8  
Old 08-19-2013
Originally Posted by karthikram
Actually my requirement is to get values from line by line in a file and assign to variable, it is good that for each line if there is separate variable also, from the above idea provided.
We get asked for this more often than you can imagine, but to date nobody's ever given a better reason for it than "it seemed like a good idea at the time". It's always silly -- how would you even use those variables? It'd take much eval madness to do a loop over variable1 ... variablen but a loop over an array is trivial.
This User Gave Thanks to Corona688 For This Post:
# 9  
Old 08-19-2013
Hi Corona,

Thanks, Let me explain the reason, we are writting scripts and our superiors want them as HTML reports,
we have some security reasons so we are not allow html packages from db side, only solution we have is through shell script ,
files which are huge in row wise as well as column wise doesnt make any sense of making awk of some minimum 20 or above in a file,

so we required two loops in line wise as well as getting the data inside the line,

i came to heard that korn shell doesnt support multidimensional array ,

atleast single dimension is possible for each line if there is separate variable that could be possible to call them in array,

Thanks anyway, If any solution by chance if found or worked Please do let me know.

And If possible anyone could give example on "eval", hopefully that could be useful to me.

# 10  
Old 08-19-2013
I get from that:
1) You have huge files
2) You must output HTML
3) You'd like multidimensional arrays

This actually sounds like exactly the kind of situation awk is meant for. It has things you can easily use as huge multidimensional arrays, and even if your lines are bigger than its line-length limit(which GNU/linux awk doesn't have, anyway) you can abuse the value of RS to read one field at a time instead.

Shell on the other hand is very poor for this. It doesn't have anything like multidimensional arrays, its performance is poor, and its variables are liable to be very limited in size.

I can show you more detail on this if you tell us more about what you want rather than details on the hoops you'd expected to jump through to do so.

Last edited by Corona688; 08-19-2013 at 01:53 PM..
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# 11  
Old 08-19-2013
Whilst I fully accord with Corona688 about better not suboptimize but take the whole picture into account to find a good solution, here's a small bashism that might do what you're so eager for:
while IFS=\| read -a WORD$((++i)); do eval echo -e WORD$i "\\\t" $\{\#WORD$i[@]} "\\\t" $\{WORD$i[@]}; done < file
WORD1      9      line1 111 22 33 44 55 aa bb cc
WORD2      13      line2 dd ee ff gg ii jj kk ll mm nn oo pp

Your file's lines will be in WORD1, WORD2,... WORDn arrays.
Not sure if and/or how this works in ksh.
This User Gave Thanks to RudiC For This Post:
# 12  
Old 08-20-2013

Thanks , the script worked well in ksh, now using your script each variable can be applied for each line ,
It is very helpful to me , But i am getting error while trying to use while loop or until after "eval" to get variable array's each element.
I will search the forum to get suitable result, meanwhile if anybody has solution it could be fine for me.
I should not expect more anyway i will workaround to get and if anyone knows Please do let me know.

$more test.txt

$more test_script_6.ksh
#! /usr/bin/ksh
while IFS=$'\|' read -A WORD$((++i)); do
eval echo -e WORD$i "\\\t" $\{#WORD$i[@]} "\\\t" $\{WORD$i[@]}
echo -e "WORD2 WORD2[3]=${WORD2[3]}"
#until [[ $j == "$\{#WORD$i[@]}" ]]; do
#echo -e WORD$i WORD$i[$j]=${WORD$i[$j]}
#j=$((j + 1))
;done < test.txt

WORD1    8       111 22 33 44 55 aa bb cc
WORD2    12      dd ee ff gg ii jj kk ll mm nn oo pp
WORD2 WORD2[3]=gg

$more test_script_6.ksh
#! /usr/bin/ksh
while IFS=$'\|' read -A WORD$((++i)); do
eval echo -e WORD$i "\\\t" $\{#WORD$i[@]} "\\\t" $\{WORD$i[@]}
echo -e "WORD2 WORD2[3]=${WORD2[3]}"
until [[ $j == "$\{#WORD$i[@]}" ]]; do
echo -e WORD$i WORD$i[$j]=${WORD$i[$j]}
j=$((j + 1))
;done < test.txt

$ksh -x test_script_6.ksh
+ WORD=0
+ i=0
test_script_6.ksh: line 3: syntax error at line 9: `$' unexpected

tried with "while" also same error.


---------- Post updated at 01:05 PM ---------- Previous update was at 12:33 PM ----------

Hi Corona,

Thanks , i will try awk RS variable too, if this is achived and there wont be any loop again,

I wil try to come up and will post for review/suggestion.

# 13  
Old 08-20-2013
Why - do you think - did I put that eval into the almost identical line 4 above your erroneous line? And, see and read again Corona688's post#8.
This User Gave Thanks to RudiC For This Post:
# 14  
Old 08-23-2013
Hi , Thanks , Now i understood that through shell it is not possible to make loop in main variable decomposing it to arrays of elements inside that each array further fetching array as array is not possible,

Please correct me if i am wrong this kind of multidimensional array and nested concept is available in PERL right.

I figured it out my script, Please let me know your suggestion or advise, how better this can be written.

$more test_script_8.ksh
#! /usr/bin/ksh

awk 'BEGIN{RS="\n";
print "<TR>";
for (i = 1; i <= NF; i++)
print "<TD>" $i "</TD>";
print "</TR>";
print "\n";
}' test.txt



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