How do I perform double substitution in bash? Post: 302305709

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Top Forums Shell Programming and Scripting How do I perform double substitution in bash? Post 302305709 by flee on Thursday 9th of April 2009 02:26:12 PM

04-09-2009

Registered User

How do I perform double substitution in bash?

Code:

#!/bin/bash
#set -x
MAX=255
FILE=$1.dns_list
#declare -a d_arr

if [ -z "$1" ]
then
          echo "Usage: `basename $0` network"
          echo "  e.g.`basename $0` 1.1.1"
          exit 
fi

echo "Remove file $FILE..."
rm $FILE

for (( i = 1; i < $MAX; i++ ))
do
    PARSE=$(host $1.${i})
        if [ $? = 0 ]
          then
             echo "$PARSE" " $1.$i" >> $FILE
        fi
done

cat $FILE | while read i
do
declare -a d_arr
ln=`echo $i | awk '{printf $5 "\t : \t" $6}' |sed 's/\.XYZ\.com\.//g'`
cnt=${#d_arr[@]}
let c=$cnt
d_arr[$c]=$ln       # <<---<<  I think I need double substitution for this stmt
echo ${d_arr[$c]}
done

# For some reason the array does not exist 
cnt1=${#d_arr[@]}
echo "The size of d_arr: $cnt1"
echo "The array ${d_arr[@]}"
exit

Hi,

How do I perform double substitution in bash?

I try to write a bash script to list all the DNS entry from a subnet e.g. 192.168.1.0/24 and store the valid DNS entry into an array ${d_arr[]},
The variable d_arr[$c] works fine in while read i loop, but once the loop finished, array ${d_arr[]} is empty, I have tried he following:

Code:

let ${d_arr[$c]}=$ln

but get a syntax error.

How do I get it store into an array for the duration when he program is still running?

Thanks,
-Fu

Last edited by rbatte1; 12-13-2016 at 09:44 AM.. Reason: Added CODE tags

flee

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rbash

RBASH(1)						      General Commands Manual							  RBASH(1)

NAME

       rbash - restricted bash, see bash(1)

RESTRICTED SHELL

       If  bash  is  started with the name rbash, or the -r option is supplied at invocation, the shell becomes restricted.  A restricted shell is
       used to set up an environment more controlled than the standard shell.  It behaves identically to bash with the exception that the  follow-
       ing are disallowed or not performed:

       o      changing directories with cd

       o      setting or unsetting the values of SHELL, PATH, ENV, or BASH_ENV

       o      specifying command names containing /

       o      specifying a file name containing a / as an argument to the .  builtin command

       o      specifying a filename containing a slash as an argument to the -p option to the hash builtin command

       o      importing function definitions from the shell environment at startup

       o      parsing the value of SHELLOPTS from the shell environment at startup

       o      redirecting output using the >, >|, <>, >&, &>, and >> redirection operators

       o      using the exec builtin command to replace the shell with another command

       o      adding or deleting builtin commands with the -f and -d options to the enable builtin command

       o      using the enable builtin command to enable disabled shell builtins

       o      specifying the -p option to the command builtin command

       o      turning off restricted mode with set +r or set +o restricted.

       These restrictions are enforced after any startup files are read.

       When a command that is found to be a shell script is executed, rbash turns off any restrictions in the shell spawned to execute the script.

SEE ALSO

       bash(1)

GNU Bash-4.0							    2004 Apr 20 							  RBASH(1)

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