Check for empty string - Shell Programming and Scripting

rahman_riyaz · #1 01-23-2008

Hello All,

I have written shell script whcih at the max 3 parameters.

When only one commandline argument and other two command line arguments are passed as empty string like

eg : archive ' ' ' '

Then i need to check whether the commandline arguments are empty or not.

i have use -n and ! -z but both of them fail for the above scenario.

Please let me know what is the alternative to solve this problem.

Thanks in anticipation

vino · #2 01-23-2008

Look for the number of command line parameters. If 1, then consider the other 2 empty.

rahman_riyaz · #3 01-23-2008

Quote:

Originally Posted by vino

Look for the number of command line parameters. If 1, then consider the other 2 empty.

Actually i need to check with one paramter and 3 paramters .

if it is one paramter then it is ok no need to check for empty strings.

But if it is 3 parameters then i need to check whether the other two are

emty since i know that there are 3 paramters.

vino · #4 01-23-2008

See this.

Code:

[/tmp]$ cat try.ksh
#! /bin/ksh


if [[ -n "$1" ]] ; then
    echo '$1'="[$1]"
else
    echo '$1' is empty
fi
if [[ -n "$2" ]] ; then
    echo '$2'="[$2]"
else
    echo '$2' is empty
fi
if [[ -n "$2" ]] ; then
    echo '$3'="[$3]"
else
    echo '$3' is empty
fi
[/tmp]$ ./try.ksh
$1 is empty
$2 is empty
$3 is empty
[/tmp]$ ./try.ksh 12 " " "  "
$1=[12]
$2=[ ]
$3=[  ]
[/tmp]$

rahman_riyaz · #5 01-23-2008

Quote:

Originally Posted by vino

See this.

Code:

[/tmp]$ cat try.ksh
#! /bin/ksh


if [[ -n "$1" ]] ; then
    echo '$1'="[$1]"
else
    echo '$1' is empty
fi
if [[ -n "$2" ]] ; then
    echo '$2'="[$2]"
else
    echo '$2' is empty
fi
if [[ -n "$2" ]] ; then
    echo '$3'="[$3]"
else
    echo '$3' is empty
fi
[/tmp]$ ./try.ksh
$1 is empty
$2 is empty
$3 is empty
[/tmp]$ ./try.ksh 12 " " "  "
$1=[12]
$2=[ ]
$3=[  ]
[/tmp]$

Hello vino,

thanks a lot for the quick reply.

The above code works if send the parameters as

sampleshellscript purge '' ''

i.e when i send null parameters.

but when i send parameters as

sampleshellscript purge ' ' ' ';

Then it does not work.

I wonder why ?that is why i was looking for an alternative to -n.

vino · #6 01-23-2008

Quote:

Originally Posted by rahman_riyaz

Hello vino,

thanks a lot for the quick reply.

The above code works if send the parameters as

sampleshellscript purge '' ''

i.e when i send null parameters.

but when i send parameters as

sampleshellscript purge ' ' ' ';

Then it does not work.

I wonder why ?that is why i was looking for an alternative to -n.

Do you mean like this ?

Code:

[/tmp]$ ./try.ksh 12 ' ' '  '
$1=[12]
$2=[ ]
$3=[  ]
[/tmp]$

rahman_riyaz · #7 01-23-2008

Quote:

Originally Posted by vino

Do you mean like this ?

Code:

[/tmp]$ ./try.ksh 12 ' ' '  '
$1=[12]
$2=[ ]
$3=[  ]
[/tmp]$

yeah exactly

when we give empty paramters as

sampleshellscript archive ' ' ' ' ;

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