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Full Discussion: Stupid question to check if variable is empty
Top Forums Shell Programming and Scripting Stupid question to check if variable is empty Post 302925922 by rbatte1 on Thursday 20th of November 2014 08:20:28 AM
Old 11-20-2014
It seems wasteful to fire up another process for this (and for incrementing counters) especially if there is an input file possibly thousands of lines long, in which case this will be expensive.

Could you try:-
Code:
if [ -z "$title" -o "$title" = " " ]
then
   echo "Null or space"
else
   echo "Contents"
fi

If this works, fit it to your script. It might be worth adjusting the loop too to something more like this:-
Code:
#Check if values in job card are not empty
grep "TITLE:" $filename | cut -d ":" -f3 | while read title         # Handle multiple records if required
do
   if [ -z "$title" -o "$title" = " " ]
   then 
      echo "10:Title Empty" ":Fail"
      ((itemfailed=$itemfailed+1))                                  # In-process
   else
      echo "10:Title description present." ":Pass"
      ((itempassed=$itempassed+1))
   fi
done >> $rptfile                                                    # All output from loop appended to this file

One thing to be aware of is that the variable being read in the loop, i.e. $title will be null when you come out of the loop. You can get round this like this if you need to know the last value:-
Code:
echo "a\nb\nc" | while read val
do
   echo "Read $val"
   VAL=$val
done
echo "\$val is \"$val\""
echo "\$VAL is \"$VAL\""

Output will be:-
Code:
Read a
Read b
Read c
$val is ""
$VAL is "c"


I hope that this helps,
Robin
 

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LEARN ABOUT DEBIAN

envstore

ENVSTORE(1)						    BSD General Commands Manual 					       ENVSTORE(1)

NAME

     envstore -- save and restore environment variables

SYNOPSIS

     envstore command [args ...]

DESCRIPTION

     envstore can save and restore environment variables, thus transferring them between different shells.

     command must be one of

     clear
	 Forget all stored variables

     eval
	 Produce shell code for evaluation, restoring all saved variables

     list
	 List saved variables in better readable format

     save variable [value]
	 Save variable either with its current shell value or with value

     rm variable
	 Remove variable from store

     Note: Only the first character of command is checked, so envstore e instead of envstore eval, envstore c for envstore clear, etc., are also
     valid.

ENVIRONMENT

     ENVSTORE_FILE  The file in which the environment parameters are stored, /tmp/envstore-EUID by default,

LIMITATIONS

     Variable names or values must not contain null bytes or newlines.

     Due to limitations imposed by most shells, it is not possible to save parameters containing more than one consecutive whitespace.	envstore
     will save and display them correctly, but unless you do IFS trickery, your shell will not be able to load them.

     The current maximum length (in bytes) is 255 bytes for the variable name and 1023 bytes for its content.

AUTHOR

     envstore was written by Daniel Friesel <derf@derf.homelinux.org>.

     Original idea and script by Maximilian Gass <mxey@ghosthacking.net>.

SEE ALSO

     envify(1)

BSD
								 December 1, 2009							       BSD
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