Bash Shell: Using the value of $A to read the value of $B ?

TIGA · 04-12-2008, 07:33 AM

hi all,

i am having problem getting the value of a variable from a txt file.

please read below and also look in the code: <*????*>

1) addresses.txt: contains "websitenames = website url"
2) test.sh: promots user to input a websitename, if the website name is found in the txt file then it will retrive the the url of that website from the addresses.txt

// addresses.txt

---------------------------------------
google=google.com
yahoo=yahoo.com
linuxQs=linuxquestions.com

---------------------------------------

// test.sh
---------------------------------------
#!/bin/bash

Name=""; #website name
Url=""; #url of the website

function get_Name {
while [ -z $Name ]; do
read -p "Enter the name: " Name;
if [ $(cat addresses.txt | grep $Name) != "" ] ; then
WorkName=$Name;
echo "website name: $Name, Url=*????*; #<< the problem part
else
echo "$Name couldnt be found in the addresses.txt, try again";
Name="";
fi
done
}

get_Name

---------------------------------------

colucix · 04-12-2008, 08:26 AM

There are a lot of ways to do this. Here is some example

Code:

url=$(gawk -F= -v name=$Name '$1 ~ name {print $2}' addresses.txt)
url=$(grep ^$Name addresses.txt | cut -f2 -d=)

Just a note on your script: using

Code:

$(cat addresses.txt | grep $Name)

is not necessary, since grep accepts a file as argument. It could be simply

Code:

$(grep $Name addresses.txt)

Also you may consider to use some other language like python (using dictionaries) or perl (using hashes). It would be easier.

ktgajowniczek · 04-12-2008, 09:20 AM

other way:

Code:

#!/bin/bash

NAME=""
URL=""
LINE=""
ADDRFILE="addresses.txt"

while [ -z ${URL} ]; do
  read -p "Enter the name: " NAME
  LINE=$(grep ${NAME} ${ADDRFILE}) && ( 
    URL=$(echo ${LINE} | cut -d= -f2) 
    echo "website name: ${NAME}, URL=${URL}" 
  ) || echo "${NAME} couldn't be found in the addresses.txt, try again" 
done

but you sholuld also be aware, that any part of appropriate NAME will work
for example "o" will work for all of the above, to avoid it you can put:

Code:

LINE=$(grep -E "^${NAME}=" ${ADDRFILE})

viron · 04-12-2008, 09:20 AM

In perl....assuming the script and addresses.txt are in the same directory.

--cut--
#!/usr/bin/perl

use strict;
use warnings;

my $file = "addresses.txt";
my %addresses;

open(FILE, "$file") or die "Could not open $file: $!\n";

foreach (<FILE>) {
chomp;
my ($k, $v) = split(/=/);
$addresses{$k} = $v;
}

sub get_name {

print "Enter the name: ";
my $name = <STDIN>;
chomp($name);

if (exists($addresses{$name})) {
print "Name: $name, Url=$addresses{$name}\n";
}
else {
print "$name could not be found in addresses.txt, try again..\n";
}

get_name();
}

get_name();
--cut--

ghostdog74 · 04-12-2008, 12:20 PM

Code:

#!/bin/bash
while true
do
 read -p "Enter name (q to quit): " name
 case $name in q|Q )break ;;esac
 while IFS="=" read -r a b
 do
    if [ "$a" == "$name" ];then
      echo "$a :$b"
      break
    fi
 done < "file"
done

TIGA · 04-24-2008, 04:19 PM

thanks a lot guys and sorry for the late replay.

i tried both shell and perl solutions. and they both worked like a charm..

i didnt expectd frequent responses, this is a great place, i think i will stick around here for some time.

colucix · 04-25-2008, 12:08 AM

Quote:

Originally Posted by TIGA

i didnt expectd frequent responses, this is a great place, i think i will stick around here for some time.

He he... welcome to LQ!

AnanthaP · 04-25-2008, 02:00 AM

TIGA (OP),
What did you actually try first before posting the code in *????* ?
End