Bash script, read file into array (Newbie)

TheMeeks · 04-13-2007, 02:19 PM

Hey, i have read the similar postings and have had no luck thus far. I have also been reading through the site for quite some time, but still no luck.

I am trying to write a bash script that will read one file line by line, into an array that i will use later in the script. the file is all text, and has one ip address per line, no ending spaces, or semi-colons, just ips.

example
10.0.0.1
10.20.0.2
10.30.20.3

any help would be greatly appreciated.

Thanks, from a grateful

wjevans_7d1@yahoo.co · 04-13-2007, 02:53 PM

How does your bash script look so far?

TheMeeks · 04-13-2007, 03:28 PM

Quote:

#!/bin/sh
echo Enter IP list, file name
read ips

exec<$ips
total=0
while read line
do
total=`expr $total + 1`;
echo $line;
done
echo Total IPs in the file $total";

I have been messing with it more, and made some progress, but not much. It is reading the file and i have it outputting the content of the file, and a total number of entries in the file. I still cant get it into an array as of yet, and the script issues a logout at the end for some reason and disconnects my ssh session.

Thanks

omnio · 04-13-2007, 04:39 PM

Quote:

Originally Posted by TheMeeks

I am trying to write a bash script that will read one file line by line, into an array

Something like this?

Code:

#!/bin/bash
# reads from the $ips file and assigns to $MYARRAY

echo "Enter the file name"
read ips

index=0

while read line ; do
	MYARRAY[$index]="$line"
	index=$(($index+1))
done < $ips

echo "MYARRAY is: ${MYARRAY[*]}"
echo "Total IPs in the file: ${index}"

Make sure your file (with IPs) ends with a newline.

Quote:

Originally Posted by TheMeeks

the file is all text, and has one ip address per line, no ending spaces, or semi-colons, just ips.

Well I guess this makes the task somehow easier.

makyo · 04-13-2007, 05:39 PM

Hi.

Bash has a construct that is similar to perl in that an assignment can handle most of the work. The perl construct is:

Code:

@a = < FILEHANDLE >;

which reads one line into each element in the array "a", but bash uses parentheses. For example:

Code:

#!/bin/sh

# @(#) s2       Demonstrate array setting.

# See http://www.tldp.org/LDP/abs/html/arrays.html for details on
# array notation.

sh --version

debug=":"
debug="echo"

SEQ=/usr/bin/seq

# Create data file - omit if you have your own external file.

cat >data1 <<EOF
10.0.0.1
10.20.0.2
10.30.20.3
EOF

a=( $( cat data1 ) )

$debug " Number of elements in array is $(( ${#a[@]} ))"
for i in $($SEQ 0 $((${#a[@]} - 1)))
do
  echo ${a[$i]}
done

exit 0

Which produces:

Code:

% ./s2
GNU bash, version 2.05b.0(1)-release (i386-pc-linux-gnu)
Copyright (C) 2002 Free Software Foundation, Inc.
 Number of elements in array is 3
10.0.0.1
10.20.0.2
10.30.20.3

See the abs, noted above for details, best wishes ... cheers, makyo

cfaj · 04-13-2007, 07:03 PM

Quote:

Originally Posted by TheMeeks

Code:

#!/bin/sh
echo Enter IP list, file name
read ips

exec<$ips
total=0
while read line
do
total=`expr $total + 1`;

In bash (or any posix shell) arithmetic is built in; you don't need an external command:
Code:
total=$(( $total + 1 ))

Quote:

Code:

echo $line;
done
echo Total IPs in the file $total";

I have been messing with it more, and made some progress, but not much. It is reading the file and i have it outputting the content of the file, and a total number of entries in the file. I still cant get it into an array as of yet, and the script issues a logout at the end for some reason and disconnects my ssh session.

Bash has a special syntax for reading an entire file:
Code:
IFS='
'
file=( $( < FILENAME ) )

TheMeeks · 04-17-2007, 08:20 AM

Thanks guys, that helped alot. Ill do my best to get through the rest of the script myself. Appreciate the help.