bash script help (arrays and strings from files)

nkoplm · 11-30-2005, 04:16 AM

i have been looking all ove trying to figgure this one out.

I have a plain text file "in.txt"

it is a new line delimitted text file filled with strings.

how can i get these strings into an array (each line of the file as a different element in the array)?

eventually i want to print a random line from the file to the screen

ex pseudo code

while true
(
echo "a random line read from my text file"
sleep 5s
)

any help?

MensaWater · 11-30-2005, 08:05 AM

bash only does one dimensional arrays. To get really sophisticated with arrays you're best off using Perl.

Having said that you could do an array with the declare built in.

Example:

Say you have a text file named "test" with the following two lines:

Code:

the quick brown fox jumped over the lazy dog
now is the time for all good men to come to the aid of their country

You could create the following simple script:

Code:

#!/bin/bash
declare -a arrtest
arrtest=(`cat test`)
echo ${arrtest[13]}

The above would make an array named "arrtest" (the delcare -a line). It would then be told to contain all the words of the two lines in the file "test" as individual elements (the arrtest= line). The last line of the script would print the 13th element which would be the word "time" from the second line of the file. (The element numbers start at 1 and count from there. The [13] is called a subscript of the array arrtest.

nkoplm · 11-30-2005, 12:34 PM

thanks for the help, but i think i need to clarify

i did not want a 2d array, just simply an array like this for "test":

MYARRAY[0] = "the quick brown fox jumped over the lazy dog"
MYARRAY[1] = "now is the time for all good men to come to the aid of their country"

so on and so forth..

dustu76 · 12-01-2005, 06:51 AM

What you want to do is go in a loop, assign each line to one element of array & keep incrementing the subscripts. The way to assign some value to to the nth subscript of array arr is:

Code:

arr[n-1]=value

HTH

bigearsbilly · 12-01-2005, 07:47 AM

this does it in perl.

Code:

#!/usr/bin/perl -w

@words = <>;
$total = scalar @words;
print $words[ int rand($total) ];

Code:

billym.>./random_word.pl /usr/dict/words
Dixieland

vivekr · 12-01-2005, 07:49 AM

Hai buddy-- how about this

Code:

#!/bin/bash
declare -a arrtest
count=`wc -l trial3 | cut -f 1 -d " "`
j=0;
i=`expr $count`
for((; i>=0 ; i--))
do
   arrtest[$j]=`tail -$i trial3 | head -1`
    j=`expr $j + 1`
done
rand1=$RANDOM
rand2=`expr $rand1 % $count`
echo ${arrtest[$rand2]}

Cheers

dustu76 · 12-01-2005, 07:57 AM

Billy, You can't use "the 800 pound gorilla"....

bigearsbilly · 12-01-2005, 08:03 AM

aw why not?
look at that! 3 lines!
lovely.

bigearsbilly · 12-01-2005, 08:30 AM

Ok then, how about Korn?
only 4096 in an array though.

Code:

#!/bin/ksh

x=$(cat $1)
set -A list $x
count=$(echo $x | wc -w )
echo ${list[$(( RANDOM % count ))]}

Code:

billym.primadtpdev>ls | ./random_word.ksh 
kbhit
billym.primadtpdev>ls | ./random_word.ksh
write.c
billym.primadtpdev>ls | ./random_word.ksh
eggs

dustu76 · 12-01-2005, 08:36 AM

The problem is that the poster wants random "line" instead of words. The code may not remain that small if you want to dispaly randomly selected full line using arrays.

Regards.

bigearsbilly · 12-01-2005, 08:43 AM

I then refer you to the perl solution.

vivekr · 12-02-2005, 06:48 AM

Big.. and dustu mine is a code that would solve the problem I think. Why dont u try that

dustu76 · 12-02-2005, 07:09 AM

@vivekr: I'm sure your code does the job. I was just wishfully wondering aloud about doing it using array in a "clever & small" shell script. Billy did it in "perl" anyway.

I think we have already answered the OPs query.

Regards.

MensaWater · 12-02-2005, 08:09 AM

O.P.?

Ron Howard was asking the question?

Brain Drop · 12-02-2005, 09:50 AM

Poor neglected tcl

Code:

#!/usr/bin/tcl
set i 0

while { [ gets stdin line ] >= 0 } {
        set aline($i) $line
        incr i
        }
while { 1 } {
        set j [ expr int( [ expr rand() ] * 10 ) % $i ]
        puts $aline($j)
        after 500
        }