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IF [ condition ] help

 
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# 1  
Old 06-03-2014
IF [ condition ] help
Hi all

Unix newbie - please be gentle

Am modifying an existing script to error trap a variable with a length of 0
Code:
#!/bin/bash

ipfile='/var/data/bin/ipaddress'

[[ -f "$ipfile" ]] && ipold="$(< "$ipfile" )"
ipnew="$( wget -q -O - checkip.dyndns.org | sed -e 's/.*Current IP Address: //;s/<.*$//' )"

# New code blocks here

if [[ "$ipold" != "$ipnew" ]]; then
  # Code
fi

If the the code
Code:
[[ -f "$ipfile" ]] && ipold="$(< "$ipfile" )"

or

Code:
ipnew="$( wget -q -O - checkip.dyndns.org | sed -e 's/.*Current IP Address: //;s/<.*$//' )"

returns an empty string, the program should exit and not go on to complete.

Please advise correct code for the new code blocks
Code:
if [[ len=${#ipold}=0 ]]; then
  exit
fi

Code:
if [[ len=${#ipnew}=0 ]]; then
  exit
fi

TIA
Last edited by CRChamberlain; 06-03-2014 at 05:07 AM.. Reason: Missing code
# 2  
Old 06-03-2014
Code:
[[ -z "${ipold}" ]] && exit

This User Gave Thanks to Aia For This Post:
CRChamberlain
# 3  
Old 06-03-2014
Aia

Thanks for your reply

Did not realise there would not be a need for an if..fi statement

Was planning to 'echo' the reason for exiting to a file and email the file to the administrator by putting code before the 'exit' in the if..fi statement.

Such as
Code:
if [condition] ;then
   echo "There is no old IP address:- "  > /var/data/bin/email2send	
  /usr/sbin/ssmtp admin@mysite.com < /var/data/bin/email2send	
  exit
fi

# 4  
Old 06-03-2014
If you are going to do more in the body of the test, by all means use the if.
# 5  
Old 06-03-2014
So the code block might look like
Code:
if [[ -z "${ipold}" ]]; then
# Code
# Code
fi

perhaps?
Last edited by CRChamberlain; 06-03-2014 at 05:41 AM.. Reason: Missing code
# 6  
Old 06-03-2014
Quote:
Originally Posted by CRChamberlain
So the code block might look like
Code:
if [[ -z "${ipold}" ]]; then
# Code
# Code
fi

perhaps?
This User Gave Thanks to Aia For This Post:
CRChamberlain
# 7  
Old 06-03-2014
Aia

Had spotted that, but thanks.

...and thanks for your solutions.
 
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