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linux command : if then fi

Hi,

it's just for a newbie question:

how to convert this basic code in sh script code of linux ?

Basic code:

Code:

if ( "$HOSTNAME" = "orion" and "$tmpvariable" = "copy" ) then

            print " Hello"

endif

I could find on the web this , but it doesnt work :-( :
Linux sh code:

Code:

#!/bin/sh

if [ "$HOSTNAME" = "orion" -a "$tmpvariable" = "copy" ]  ; then

            echo " Hello"

fi

Thank you :)

That script works like a charm. You just need to make sure that your variables are exported.

export tmpvariable

also assuming that you've set execute permissions on the script

chmod +x <scriptname>

best of luck!

Works here ... maybe the variables haven't been exported properly?

Cheers,
Tink

P.S.: Heh - beat by a couple of seconds...

That should work!
Anyway, you may want to try this:

Code:

if [ "$HOSTNAME" == "orion" ] && [ "$tmpvariable" == "copy" ]; then

  echo " Hello"

fi

Yves.

Quote:

Originally Posted by theYinYeti

That should work!
Anyway, you may want to try this:

Code:

if [ "$HOSTNAME" == "orion" ] && [ "$tmpvariable" == "copy" ]; then

  echo " Hello"

fi

Yves.

Thank you for so much replies and so fast !

I have two questions.

In my script, I should then add export:

Code:

#!/bin/sh

echo "enter the variable 01"

read tmpvariable

export tmpvariable

if [ "$HOSTNAME" = "orion" -a "$tmpvariable" = "copy" ]  ; then

            echo " Hello"

fi

Hostname is already exported.
I dont really know why the export is very necessary yet. Actually why is it needed in such example ? :scratch:

I just tried thsi:

Quote:

#!/bin/sh
echo "enter the variable 01"
read tmpvariable
HOSTNAME="orion"
#export HOSTNAME
#export tmpvariable
if [ "$HOSTNAME" = "orion" -a "$tmpvariable" = "copy" ] ; then
echo " Hello"
fi

this one is working.

and my second question is :

Code:

[ "$HOSTNAME" == "orion" ]

Code:

if [ "$HOSTNAME" = "orion" ]

we can find both form, it's different than in basic. More flexible.
Which form is better to be used with = or == ?
What's the difference ?

this one :

Quote:

if [ "$HOSTNAME" = "orion" ] && ["$tmpvariable" = "copy" ] ; then
echo " Hello"
fi

says " COMMAND not found" :( :-(

and this alternate one:

Quote:

#!/bin/sh
echo "enter the variable 01"
read tmpvariable
HOSTNAME="orion"
#export HOSTNAME
#export tmpvariable
if [ "$HOSTNAME" == "orion" ] && ["$tmpvariable" == "copy" ] ; then
echo " Hello"
fi

says " COMMAND not found" line 7 also :( :-(

non working one:

Quote:

#!/bin/sh
echo "enter the variable 01"
read tmpvariable
HOSTNAME="orion"
export HOSTNAME
export tmpvariable
if [ "$HOSTNAME" == "orion" ] && ["$tmpvariable" == "copy" ] ; then
echo " Hello"
fi

That was very interesting !! Thank you !!

Quote:

Originally Posted by Xeratul

Thank you for so much replies and so fast !

I have two questions.

In my script, I should then add export:

Code:

#!/bin/sh

echo "enter the variable 01"

read tmpvariable

export tmpvariable

if [ "$HOSTNAME" = "orion" -a "$tmpvariable" = "copy" ]  ; then

            echo " Hello"

fi

Hostname is already exported.
I dont really know why the export is very necessary yet. Actually why is it needed in such example ? :scratch:

No, not in this example; but in your first attempt there was no
mention of the variable being defined; and if it's supposed to
be picked up from the environment it has to be exported.

Quote:

Originally Posted by Xeratul

I just tried thsi:

this one is working.

Defined in same scope.

Quote:

Originally Posted by Xeratul

and my second question is :

Code:

[ "$HOSTNAME" == "orion" ]

Code:

if [ "$HOSTNAME" = "orion" ]

we can find both form, it's different than in basic. More flexible.
Which form is better to be used with = or == ?
What's the difference ?

== is definitely better form :}

Cheers,
Tink

Ahhhh !! I understand !

Code:

#!/bin/sh

echo "enter the variable 01"

read tmpvariable

HOSTNAME="orion"

if [ "$HOSTNAME" = "orion" ] &&  [ "$tmpvariable" == "copy" ]  ; then

            echo " Hello"

fi

is working great !

Code:

#!/bin/sh

echo "enter the variable 01"

read tmpvariable

HOSTNAME="orion"

if [ "$HOSTNAME" == "orion" ] &&  [ "$tmpvariable" == "copy" ]  ; then

            echo " Hello"

fi

is working great too !

I found why the one there is not working:
Because only of the space too close :

Quote:

#!/bin/sh
echo "enter the variable 01"
read tmpvariable
HOSTNAME="orion"
export HOSTNAME
export tmpvariable
if [ "$HOSTNAME" == "orion" ] && ["$tmpvariable" == "copy" ] ; then
echo " Hello"
fi

damn, we have to be very very careful with spaces !
that's very quick to make a mistake.
I think even before == we should add space char.

and working too :

Code:

#!/bin/sh

echo "enter the variable 01"

read tmpvariable

HOSTNAME="orion"

if [ "$HOSTNAME" == "orion" -a  "$tmpvariable" == "copy" ]  ; then

            echo " Hello"

fi

Thank you very much !!
I learned a lot !

and sometimes we can see that there is [[ ]] double
what could be the deep purpose or use with this .. ?
I tried but had some troubles (nothg was working )...
via : if [[ "$HOSTNAME" == "orion" ]] ; then
bla bla

Quote:

#

Avec la version 2.02, Bash a introduit la commande de test étendue [[ ... ]], réalisant des comparaisons d'une façon familière aux programmeurs venant d'autres langages. Notez que [[ est un mot clé, pas une commande.

Bash considère [[ $a -lt $b ]] comme un seul élément, renvoyant un état de sortie.

Les constructions (( ... )) et let ... renvoient aussi un état de sortie de 0 si les expressions arithmétiques qu'elles évaluent se résolvent en une valeur non nulle. Ces constructions d'expansion arithmétique peuvent donc être utilisées pour réaliser des comparaisons arithmétiques.

let "1<2" renvoie 0 (car "1<2" se transforme
en "1")
(( 0 && 1 )) renvoie 1 (car "0 && 1" donne "0")

This script:

Quote:

#!/bin/sh
echo "enter the variable 01"
read tmpvariable
HOSTNAME="orion"
if [[ "$HOSTNAME" == "orion" -a "$tmpvariable" == "copy" ]] ; then
echo " Hello"
fi

Says : syntax error

Also,

Quote:

Perform a mkdir if a directory does not exist:

test ! -d tempdir && mkdir tempdir

this is meaning that we'll have an if ... then ... else
it's kind of like a simple if ... then ...fi

Quote:

commande1 && commande2
Exécute commande2 si et seulement si commande1 s'est bien déroulée. Généralement utilisé dans les conditions des structures if, while et until.

I don't have time for a good answer. Meanwhile, just one tip: don't forget the spaces around [ and ].

Yves.

Quote:

Originally Posted by chrism01

Here's a bit about -a vs && :
http://www.dartmouth.edu/~rc/classes...ests2.html#top
See also here for [ ] vs [[ ]]
http://www.tldp.org/LDP/abs/html/tes...ml#DBLBRACKETS

Thank you very much for your Both Support in SH programing !!

(I have to debug it now ... :-) :-) ) (errors errors...)

To be continued

Greetings !