topic Re: Shell Script Help in Operating System - HP-UX

Shell Script Help

SSP_1 — Wed, 08 May 2002 08:22:58 GMT

Hi ,

I have a shell script written , having 2 nos of commnads to execute. Here I have to define a condition for the execution so that if the first command is successful then only second will get executed.

Pl help !!!!

Re: Shell Script Help

Deepak Extross — Wed, 08 May 2002 08:27:26 GMT

command1 && command2

command 2 will only get executed if command 1 is successful. See man sh-posix for details.

Re: Shell Script Help

Sukant Naik — Wed, 08 May 2002 08:28:56 GMT

Hi Sripad,

Do something like this.

#!/usr/bin/ksh
command1
if [ $? -eq 0 ]
then
command2
fi

Re: Shell Script Help

Deepak Extross — Wed, 08 May 2002 08:30:14 GMT

Or you could try the more readable form:
command1
if [ $? -eq 0 ]
then
command2
fi

Re: Shell Script Help

John Palmer — Wed, 08 May 2002 08:31:05 GMT

Another way is:-

if command1
then command2
fi

Regards,
John

Re: Shell Script Help

SSP_1 — Wed, 08 May 2002 08:37:08 GMT

Hi ,

In "if [$# -eq 0] then" what does "0" corresponds? I believe it's "false" so doesn't this condition mean "if exit status of my previous commnad is "false" then execute second one".

OR should I have to specify "1" instead of "0".

Re: Shell Script Help

Deepak Extross — Wed, 08 May 2002 08:38:53 GMT

In unix, a return value of 0 indicates success.
So [ $? -eq 0 ] is a test of successful execuation of the preceding command.

Re: Shell Script Help

Deepak Extross — Wed, 08 May 2002 08:47:24 GMT

Also have a look at this thread -
http://forums.itrc.hp.com/cm/QuestionAnswer/1,,0x96b70bce6f33d6118fff0090279cd0f9,00.html

Re: Shell Script Help

Peter Kloetgen — Wed, 08 May 2002 08:53:06 GMT

Hi,

this is very easy, you even don't need to test anything like return code:

first_command && second_command

--> second command will only be executed, if first command has a return code value of zero

first_command || second_command

--> second command is only executed, if first command was not successful, has a return code not equal zero.

If second command is executed later in the script, you have to put the return code of first command as value into a variable, cause return code is overwritten each time, a new command is executed:

first_command

var=`echo $?`

Then, if the second command has to be executed, check out the return code of the first command:

if [ $var -eq 0 ]
then
second_command
fi

Allways stay on the bright side of life!

Peter

Re: Shell Script Help

V. V. Ravi Kumar_1 — Wed, 08 May 2002 08:59:16 GMT

hi,

u can check the success or failure of the command, include an echo statement.

when a command successfully executes "echo $?" should show "0" else it shows "1".

in ur case

command1
if [ $? -eq 0 ]
then
command2
fi

regds
ravi